As it happens, I have some experience and ideas about this issue, albeit from a singular PC perspective, since it is relevant for my old PC and my plans for a revised/optimized revival of the character. In my old group, I was a player and assistant SG in charge of rules and setting issues; so I had a great degree of authority on such concerns. What follows is a back history and life plan that broadly covers the mage’s career to immortality and beyond. Part of this we achieved in play; part is planned character development (or retrospective revision) when I get an opportunity to continue the story.
IMS we dropped character creation limits to Major Hermetic Virtues, Minor Personality Flaws, and Story Flaws as dysfunctional to creative freedom. Fertile Longevity Ritual and Subtle Opening breakthroughs are widely available. It is unheard for a mage or their apprentice to waste time copying books, since every covenant has skilled and trustworthy scribes that know Magic Theory and the four Realm Lores as well as illuminators and bookbinders to take care of the task. Suspicion and prejudice about Diedne stuff almost entirely faded away; it is no more a relevant issue for the Order. The other breakthrough and magitech advancements described in this thread are a fuzzy issue.
PC is a generalist mage, spontaneous-only specialist, Mystagogue, Seeker, and would-be immortal. His approach to magic is shaped by having Cailleach Magic, LLSM, Chthonic Magic, Faerie Magic, Subtle Opening, SFB (Sidhe), Rigid Magic, and Unstructured Caster. He is Ambitious, Pagan, and a Seeker, got a Covenant Upbringing, and has a Lesser Malediction about painful contact with iron and holy objects. He easily acquired Comprehend Magic, Mythic Herbalism, Persona, Second Sight, Shapeshifting, and Sihr thanks to Subtle Opening and SFB. Just like Chthonic Magic, he deemed he could get away with having the Goetic Arts if he was cautious with their use. Therefore, he learnt Ablating, Binding, Commanding, and Summoning (Spirit) the same way.
He originally was Ex Miscellanea, but switched to Merinita soon after apprenticeship. Both Houses have enough of a loose approach to membership that the transition took place without much controversy on both ends. In fact, both Houses are content to let him claim de facto dual membership most of the time. He is equally at ease with belief, practices, and environment of both Houses. He is not careless about management of House Mysteries, but neither he is stingy or paranoid about them.
I had him switch to Merinita since I found most of its House Mysteries of considerable relevance and usefulness for his approach to magic. He eagerly initiated Animae Magic, Arcadian Travel, Charm Magic, Glamour, Spell Timing, and Unaging (surely faerie-like enough to fit in Merinita mysteries and have scripts for it). He mostly used canon scripts when available, except I found Harmless Magic and Social Handicap too dysfunctional and burdensome for his concept. Therefore, I replaced them with Faerie Metamorphosis and Warped Magic (dreamlike). Consecrated ground seemed an appropriate choice for Vulnerable Magic. The PC also unearthed an old Diedne script for Hidden Ways and Places, adapted it to Merinita Lore and self-initiation, and used it. It is a Minor Virtue that works as an analog of Arcadian Travel for paths and regios associated with the Magic Realm. Details are in Sub Rosa #13, except Merinita Lore replaces Diedne Lore and Comprehend Magic can be a substitute of Magic Sensitivity. The Ordeal was Motion Sickness, as in the original script.
He also initiated a ‘Wild’ version of the Gentle Gift that has Offensive to Divine, Infernal, and Human Beings as an Ordeal. Past communication with the author of HoH:MC told me this combo is valid, the Ordeal is worth two Minor Flaws, and scripts for it exist in the House. Adding Unbearable to all three would have been just as valid and the equivalent of a Major Flaw. However, I deemed having the equivalent of the Blatant Gift was too much trouble. Building on that, he also initiated Alluring to Faeries and Alluring to Magical Beings. Binding the Gift seemed icing on the cake about having an optimized familiar and being a social god with faeries and magical beings, but probably good enough to acquire after he got Spirit Familiar and could get a companion to his tastes.
I am still uncertain whether Mystical Choreography (surely of significant usefulness to PC) fits in the Merinita bag of tricks, and whether Performance Magic (Music) (certainly faerie-like enough) is worth the initiation effort for him. As a rule, he is not the subtle kind of mage and tends to avoid mundane society and the Dominion. I also wonder if MC would be worth the effort of self-initiation through Principles Lore, since the Jerbiton are not a Mystery House and hence unlikely to have scripts for the Virtue. As far as I can tell, however, they are not going to care if another mage gains it.
I decided Nature Lore was inferior to Ways of the (Land) and the other nature mysteries were of little use to him. Therefore, he initiated Ways of the Forest, with Ordeals making him even more avoidant of cities and the Dominion (Deleterious Circumstance (in a city) and Divine Stigmatic). Susceptibility to Divine Power was thematic but seemed too inconvenient since he expects the Divine to be a recurrent enemy. I am uncertain whether adding Ways of the Mountain and/or less likely Ways of the Plain or Ways of the Seawould be worth the effort. These Virtues combined would cover the vast majority of terrain in Mythic Europe. However, Ways of the Forest alone already covers a great deal of land in 1220, and he loves the woods. Ways of the Town is obviously inappropriate, and I am doubtful he is going to spend enough time in the Arab world for Ways of the Desert to be useful. I deemed Story Magic was of little value to the character. Symbolic Magic and Perpetuity are useless to the PC given his inability to use ritual magic, and I would not touch Unnatural Magic with a 10-foot pole.
I eventually plan for him to gain access to ritual effects by pursuing the Quick Charged Items and Ritual Items breakthroughs. He could not care less about the loss of formulaic magic, finding it too inflexible, dependent on unwelcome long-term preparation and planning, and a source of choice paralysis. He prefers to get by through a mix of optimized spontaneous magic, enchanted devices, and other supernatural powers. However, he acknowledges inability to use ritual magic is a serious handicap he plans to remedy.
He is greatly interested in becoming immortal, but Becoming seems quite dysfunctional for a spontaneous specialist. Therefore, he is going to pursue the path of alchemical immortality combined with Spirit Familiar, Inscription on the Soul, and Durable External Soul. He loves going on Seeker adventures and sensual pleasures too much for Living Ghost or Ascension to the Hall of Heroes to be good options. Theoretically speaking, however, I have a few ideas to supplement Living Ghost with other resources to make it an acceptable, if suboptimal, alternative. These include using a living corpse, enchanted devices for instant travel to the Haunt, and Canaanite Magic.
As it concerns Bjornaer mysteries, I was greatly interested in adding Sensory Magic to the PC bag of tricks, also b/c the Virtue seems thematically fitting for Merinita mysteries. The affinities with Glamour are obvious, and it seems a rather faerie-like power. I am not too concerned about the Bjornaer getting upset, since the Virtue only has loose affinities with the rest of their House Mysteries. It has relatively broad scope for Hermetic magic well beyond the Heartbeast stuff. In fact, it would have been part of the standard system if only Birna and Bonisagus had been a little more efficient about integrating it. It is quite plausible a Merinita Mystagogue might independently re-invent it. As far as I can tell, a non-Bjornaer can use the Virtue fine as long as they ignore Heartbeast references, and you can use the canon script with few adjustments.
As it concerns actual acquisition of the Virtue, it might indeed happen by reverse engineering, or by the PC persuading a Bjornaer to share it in exchange for some other valuable secret. In the case the House might indeed get seriously upset about the issue, the PC may well keep his knowledge of the Virtue a secret (as he does with Chthonic Magic and the Goetic Arts) until he is too powerful and/or too popular in the Order thanks to his Seeker achievements to fear Bjornaer retribution. As it happens, the PC acquired it in a roundabout way.
I could not care less about the rest of the Bjornaer mysteries, since I find the combo of Shapeshifter, an optimized familiar, Great Elixir, and IotS superior to all of them. The PC regards House Bjornaer as a potential good ally of Merinita and Ex Misc. to protect Faerie and Magic beings and places from mundane and Dominion encroachment. He is the Merinita/Ex Misc. equivalent of a Wilderist, and could not care less for what the Jerbiton or Christian/Muslim mages hold dear. However, he has little sympathy or patience for Bjornaer obsession about ancestors, paranoia about shapeshifters, and dislike of faeries.
As it concerns Verditius Mysteries, the PC has serious interest to acquire Bind Magical Creatures when he masters alchemical mysteries in his path to immortality. I deem it a good complement to Hermetic Alchemy and Major Philosophical Alchemy, and a less risky alternative to Ablating for seizing supernatural powers. More or less the same points I made for SM and Bjornaer apply for BMC and Verditius. The other Verditius mysteries have little interest for the PC. Becoming a competent enchanter is a secondary pursuit for him to help replace formulaic magic (as well as ritual spells with appropriate breakthroughs) and/or a welcome side benefit of his quest for alchemical immortality. I dislike being too reliant on tools, and I frown on most of the Ordeal prices Verditius mages pay for their secrets. At most, I might be interested in Reforging Enchanted Items, but only if I get to change the canon Ordeal, since being unable to experiment does not fit the concept. As a rule, the PC tends to have a rather businesslike relationship with this House.
As it concerns Criamon stuff, I have zero interest in their beliefs and practices, or the vast majority of their Mystery Virtues, and I find the PC’s abilities often are adequate replacements for them. Theoretically speaking, I might have some potential interest in the Spiritual Nourishment and Repose stations in Path of the Body. At the very least, however, I would have to avoid or remove the Ordeals that turn you into a true believer, since I dread getting shackled by them. The PC tends to find the Criamon tiresome and incomprehensible, if not necessarily malevolent, and best left alone.
As it concerns the rest of the character’s development, besides doing all the Merinita stuff mentioned above, he got involved in the Adamic language, Ptolemaic Coordinates, Conciatta’s, Fortunata’s, and Herisson’s quests, as well as gathering insight material for the Fertility Magic, Rune Magic, Folk Witch, and Learned Magicians breakthroughs. He mastered Adamic language and Ptolemaic Coordinates, and studied Principles Lore as his versatile self-initiation tool for anything that would not fit in Merinita Lore. He initiated Spirit Familiar (and avoided getting a familiar until he unlocked this option) and Puissant Principles Lore, but had no interest in the rest of Fortunata’s scripts. I planned for him to get a different kind of Focus and a better option for access to ritual effects than torturing and draining captive spirits. The other insight gains needed some serious lab work to be useful, so he put them on the backburner. In this regard, his top research priority is to acquire the Quick Charged Items and Ritual Items Virtues to remedy his ritual deficiency, but he eventually plans to unlock all of these breakthroughs as well as Hermetic Realm Initiation.
Another notable achievement was defeating a corrupt Children of Hermes offshoot and raiding their script library. We got ample leeway from the SG about choosing the scripts we got, as long as we kept it at a half-dozen per character or so and mostly Minor Virtues. My choices included Bjornaer derivatives for Cautious Sorcerer and Sensory Magic, Green Cockerel derivatives for Hermetic Alchemy and Lesser Elixir, a Disciples of the Worm derivative for Inscription on the Soul, and a script of uncertain origin (perhaps a Flambeau mystae) for Major Magical Focus (Damage). As assistant SG in charge of rule issues, I decided Vulgar Alchemy, Planetary Magic, and Names of Power are an utter waste of time and effort, and best expunged from the system IMS. We replaced them with Hermetic Alchemy, Celestial Magic, and Invocation Magic respectively without any need for prerequisites.
More importantly, my share of the booty also included scripts from a ‘Cult of Hermetic Excellence’ (a mystae offshoot of Bonisagus) about becoming a ‘Hermetic Prodigy’ (a Major Virtue package of Book Learner, Free Study, and Study Bonus) and a ‘Research Prodigy’ (a Major Virtue package of Affinity with Magic Theory, Inventive Genius, and Puissant Magic Theory). Ordeal choices for the former were Ability Block (Martial Abilities) and Master of None. Ordeal choices for the latter were Exciting Experimentation and Prone to Chance. There also was a script for becoming a “Prodigy Student” (a Major Virtue package of Apt Student, Good Teacher, and Independent Study) with Unspecialized and Weak Scholar as Ordeals. Cautious Sorcerer and Sensory Magic scripts had no Ordeal as per canon examples. Inscription on the Soul had an Ordeal of Deleterious Circumstances (when not touching talisman), due to its affinity with the Consummate Talisman Virtue. The Ordeals for the Focus script concerned coming under greater influence of Mars, which meant a combination of Ambitious (raised to Major in the PC’s case), Lecherous, and Wrathful.
I am skeptical about sanctioning astrological Virtues as a strict prerequisite for alchemical immortality. However, I acknowledge Celestial Magic may be a valid optional addition to Major Philosophic Alchemy and Bind Magical Creatures in an alchemical mystery path to improve enchantment proficiency. Therefore, the PC is going to get an opportunity to acquire these Virtues in the late phase of his quest for immortality.
My Ordeal ideas for these other Virtues and Great Elixir include Environmental Sensitivity (bad air), Magic Spirit Companion, Nocturnal, Viaticarus, Vulnerable to Folk Tradition, and Weak Magic Resistance (touching filth), as extensions of the concepts of alchemical purity and the character becoming a supernatural being. Canon scripts for BMC include no Ordeal. PC adapted all of these scripts to Principles Lore, used them, then went on an extended reading spree to boost his Arts and Abilities and make up for all the time spent on adventures and initiations. He also adapted these scripts and Fortunata’s one for Spirit Familiar to Merinita Lore, since he deemed them valid additions to the House’s body of knowledge.
He hopes he can drive House Merinita to welcome addition of the alchemical immortality path to its body of lore as a potential alternative to Becoming for mages like him. He would be glad to help spread his preferred approach to Hermetic magic by developing Merinita and Principles Lore scripts for spontaneous-boosting Virtues with Ordeals that penalize formulaic magic, esp. since suspicion of Diedne-like stuff has faded from the Order. At least Poor Formulaic Magic; Rigid Magic and Unstructured Caster if he can get away with it. Much the same way, in all likelihood he would attempt to drive mages interested in his Mystagogue assistance to turn their backs on the Dominion and help protect Faerie and Magic places and beings by using Pagan, Depraved, and/or appropriate Vows or Prohibitions as Ordeals.
When he deems he has raised his Arts and Abilities scores enough, or simply gets tired of reading all the time (managing the effects of Master of None is easy for a generalist), he is going to pursue breakthroughs from the insights he got. As it concerns adventures, he is almost surely going to complete the round of Ancient Magic, Legends of Hermes, and Mythic Locations quests. Even if he is not necessarily or even likely interested in all of their rewards, they might appeal to cabal mates, and most of them seem fun and interesting experiences.
Then there is studying even more, becoming an alchemical immortal, and complementing the Great Elixir with Durable External Soul by persuading or forcing the Koldun to share their secrets. The combination of GE and DES promises excellent synergy for immortality. As it concerns Durable External Soul, I suppose Supernatural Nuisance and Visions might be good Ordeals. External Soul seems best initiated with no Ordeal since the script is supposed to be repeatable if the stone gets destroyed. Of course, it also depends on which sequence the PC uses to initiate these Virtues since Ordeals are inappropriate for immortals. OTOH, they have unlimited time to pile up Quests.
After getting immortality, other long-term projects include complete Hermetic integration of the various Hermetic and Supernatural Virtues he got, mastering an easy way to heal without vis even beyond the options Rune Magic may offer (Hyperborean magic looks like a promising line of research in this regard), and developing several magitech improvements detailed in Transforming Mythic Europe. Moreover, he hopes to find a way to cripple the Church and marginalize the Dominion or at least push it back to being an option among many in the marketplace of religion for those who really want it.
He loathes what he sees as the implacable exclusivism and tyranny of the Divine even if he equally despises the overwhelming drive of the Infernal to create misery for its sake. In favorable circumstances, however, he is not averse from opportunistically using infernally tainted powers and resources, as shown by his use of Chthonic Magic and the Goetic Arts when he thinks he can keep the Order in the dark. The Maleficia, however, seem to come with too much baggage, no matter their undeniable usefulness. Stealing the demonic power that conceals Infernal taint from magic scrutiny with Ablating or Bind Magical Creatures seems a promising option to cover his tracks in this regard. However, he is not ever going to cooperate knowingly with the forces of Hell. As it concerns tapping Divine powers and resources, he deems they come with too many behavioral constraints to be an acceptable option.