There is nothing that restricts those guidelines to Quaesitors at all. It should also be noted, that just because a guideline isn't listed, doesn't mean it can't be used. Some may disagree with me there, but I would point out that the very core book does this repeatedly.
Which is why I made the spell guidelines pdf, available on the Atlas site. David only wanted generally useable guideline in it, not ones that required special Virtues or similar. I still have a bunch of more recent books to get and check through for further guidelines, but the pdf is fairly complete because most came out way back when.
Look at Disenchant on page 160 of the core book. It's a ritual. The core book itself uses rituals for undoing enchantments.
Consider the following as well. You're saying Quaesitors have better access to dispelling than the regular magus but the regular magus can do it far more easily with the basic guideline. If you can do it with the basic guideline, why do the Quaesitors, with their special access, need a ritual?
Now you're starting to see some of the fun things that can be done with a longevity specialist pc.
If you're good enough, you could also make longevity rituals for two or three people in the same season. Let's say you can manage a total of 100. Mercere pays for 10th-magnitude rituals, and you could do two at once. You could give them a discount but still charge more than you would for a single ritual.
How does that work? From Core (emphasis mine): "The ritual takes a season, and culminates in some sort of focus, which is appropriate to the magus in question...The Longevity Ritual takes one season to develop and perform, and the subject of the ritual must be present for the whole of that season." ?
The text on Multiple Laboratory Activities specifically says (emphasis mine): "Sometimes you may wish to perform laboratory activities that, though rewarding, are well within your capabilities and do not each require an entire season of effort."
While a LR specialist may well have the Lab Total to wish she could split it, the wording on the LR section does not allow it.
Is there errata for this?
(hoping not to derail this thread with this question).
The one I'm working on? I've been thinking youth and immortality, trying to cover longevity as well as the elixirs. However, I do like aging since you can also use it to bring things to maturity quickly, which can be handy with plants and animals.
I'll look into it; I could be wrong. I would note that even that level-2 spell you want to develop takes an entire season. But it doesn't take all your effort for that season, leaving you room to develop several more over the whole season, each of which takes the whole season. So the rules definitely distinguish between the activity taking the season and the amount of work you can do in a season.
Edit: OK. Got it. Those same rules state they can work for potions. And yet potions (and other charged items) say,
So just finding this comment about spending a season doesn't rule out longevity rituals. As I said with spells, they take the season, too. There is a difference between the amount of work you can do and the time. For a modern example, let's say you're growing a typical plant. You could have lots of tools at your disposal so you can grow more at the same time, but they each still require their own time to grow. That you can handle more doesn't mean they take less time.
That's the opening of the whole section, up to Fenicil's Rituals. The guideline is part of the Quaesitorial Magic, that's the intention there. It's different from the Core, sure, but the core guideline requires the wizard to know the magic, and the Quaesitor one does not. That would mean the Quaesitor version could get around limitations the general doesn't. It's a small benefit, and I'm hard pressed to think of an example that fulfills it, but it's there. shrug
Please read that quote again. Did you note that the very thing you quoted states that that statement is about investigative magic? Have you also not yet seen that Disenchant is a ritual in the core book, despite my having referenced it twice? Are you saying that core book ritual is a Quaesitor secret? Are you saying it's not a ritual? Are you saying the Quaesitors have secret special magic to make themselves worse and it's a crime for anyone else to make themselves worse?
Besides which, just because a spell's text isn't shared, doesn't mean the guideline isn't useable by others. If you don't believe me, look at the CrMe/Co rituals and check the core guidelines. And I only spoke of the guideline not being restricted.
Similarly, do you let anyone cast forceless magic, or just Quaesitors. If anyone, then you're being inconsistent in interpreting that opening statement since forceless casting is also in that section. And I'm pretty sure other books allow for other magi casting forceless magic even though it is presented in this section.
Forceless casting is a sidebar, those can get moved all around in a chapter. It's not necessarily specifically part of Quaesitorial Magic, but that's where the sidebar was put, probably because it's more Hermetic casting than Fenicil's Rituals and applied better to the Quaesitor section than the Mercere or Bonisagus chapter. That's just my experience with how sections of a book can get shuffled. If it were specifically part of Quaesitorial Magic, it wouldn't have been put in a sidebar, it would have had a header, like Acute Sense or Sigils & Traces-- these are elements of Quaesitorial Magic. The "Spells & Guidelines" are a subheader of Quaesitorial Magic, that means that section is a part of Quaesitorial Magic.
You don't have to treat it that way if you don't want to, but the way it's outlined, those guidelines are Quaesitorial Magic, the way the Mutantum Magic in the Mercere chapter is for a magical Mercere or a descendent. Just because it's PeVi doesn't mean it's not part of the Quaesitor's tool box.
The Minor Focus example in ArM5 is healing, so if you did Longevity, you'd hit aspects of healing, or Vigor, but probably not Fertility.
Honestly, I'd be ok with Healing, because then the wizard would be good to have other non-Longevity rituals where their MMF would be useful. Being more restricted than Healing wouldn't be necessary in our troupe; I'd be interested to hear the argument for why it shouldn't be Healing.
1: Healing already covers a ton of CrCo, CrAn, and CrHe. There isn't that much in CrCo it doesn't cover, and then you get all that other stuff. It may apply to some other things as well (healing an elemental?). So it's already pushing hard against the limits of Minor Magical Focus.
2: If you allow healing to cover longevity rituals as well, you'll encourage design convergence. Those interested in CrCo have little reason to choose anything else. If you leave longevity rituals out, there are more viable options for those interested in CrCo, so you'll get more variety in the world.
3: Preventing decay/damage is not the same as undoing it. Stopping someone from aging is not the same as healing someone from an Aging Crisis. If you look up healing, you'll see its about making someone healthy/whole (again), as opposed to keeping someone healthy/whole. If prevention and undoing fall in the same category, would you let someone use the Healing mMF for Ward Against Heat and Flames?
The core rulebook says I can invent a spell listed there or invent a spell from a spell listed there (p.95), which are the same thing as using its guideline, just letting you start partway through the process to save some effort. Disenchant (p.160) is listed without restrictions for anyone. It's one of the core book spells, so it's one even the most restrictive campaigns I've ever seen allow any starting magus to have. GotF also call Disenchant, among others, a "standard spell" (p.56). Now, Disenchant uses a guideline not explicitly listed in the core book, but the core book itself says I can build off of that spell, so it necessarily implicitly says I can use that guideline to design a spell. So the implicit guideline Disenchant uses is fair game for any magus. Well, this very guideline that was later published in the Guernicas section of HoH:TL (p.75). So the core book itself says I can use this guideline from the Guernicas section of HoH:TL. The core book does not, however, say the Quaesitors will share their lab texts with me.
So the core book says I can use one of those guidelines. You say I can't. That would seem to indicated a problem with your interpretation of what is stated.
Again, read what your quote says. It does not restrict guidelines. It restricts the lab texts. Those texts are what are classified as house secrets.
Now, there is a spell built off of non-Hermetic stuff that you could separately argue others cannot design until they learn that special bit, either by learning Fenicil's ritual or by learning that spell.