Hedge Magic (Revised) introduced the Limit of Magic Resistance as a theorical Limit of Magic, one that has been proven false only the Order of Hermes. Reading the different hedge magic traditions from Hedge Magic (Revised) and Rival Magic, as well as the Saihr from The Cradle & The Crescent, one can note that there are some things that one traditions can't do that others can (example: Learned Magicians can't bind Familiars, while both the Order of Hermes and the Folk Witches can).
So, what Limits of Magic do you think would be present in their (Hedge Magic) Theory to explain why they can't do something? Even if they suspect that's actually an error in the theory?
Well, part of the problem is that many Hedge Traditions don't really have any Magic Theory equivalent and are thus limited to a particular set of stock effects. IIRC, Folk Witches, Vitkar, Amazon Sorceresses, and Virgilian Wizards are the only Non-Hermetic traditions sophisticated enough to have a working framework with which to understand their magic and its limitations...
But imagining either one of these, or that the other Hedge Traditions somehow produce a great theorist who has a Breakthrough and develops a (Hedge Magic) Theory. Is there anything in their tradition that they can't do that they would explain the as a Limit of Magic?
Other systems aren't meant to be universal though, they have all sorts of limits - The Elementalists, for example, are limited to being unable to affect anything that's not an element, humour, or elementally aligned supernatural being, but I'm not sure that could really be called a Limit of Magic in any meaningful sense.
Are you perhaps thinking of something more in the vein of suggestions for how the various traditions might be able to overcome some of the shortcomings inherent in their magical styles?
No, I'm talking about how a tradition (any of them) would interprete the shortcomings inherent of their magical styles, about how they would explain why they can't do something. If a hedge magic were to train a new apprentice and start explaining what they can and can't do, how they would explain their style's shortcomings. They aren't suposed to be real Limits of Magic, only what a hedge magic would believe or suspect is one, even if only to explain why doing something is impossible for them. Like the Limit of Magical Resistance is not a real Limit of Magic, only something most traditions would suspect being a Limit of Magic, as they don't know about Parma Magica.
Elementalists: All of the below are manifestly flaws in Elementalist Theory since other magic users can ignore them.
Limit of Effort: Affecting a target with proactive magic (any Technique other than Divining) always requires that the magician either expend Fatigue or spend a season of effort in his lab working his magic.
Limit of Range: It is impossible to use Summon beyond Touch, Controlling beyond at other than Voice, or to otherwise alter the standard RDT employed in the standard practices of Elementalist Magic.
Limit of Type: Due to the unique nomenclature they employ, Elementalists may affect bodily humours and spirits with their magic as well as elemental. The downside is that each of these are affected separately.
Folk Witches: Again all of the below are clearly flaws in Folk Witch theory. Since they possess their own MT variant, however, they are likely to be aware of this and possibly even working on a way to remedy the situation.
Limit of Enchantment: While capable of imbuing Ritual effects into enchanted items, Folk Witches have no way of creating fetishes or potions without expending Vis even if the power itself doesn't require it.
Limit of Specialization: Folk Witches are unable to use their Supernatural abilities in the standard manner (not employing Fetishes, Incantations, or Potions), occasionally to their detriment.
Limit of Kitchen Work: Folk Witch labwork requires a seasons and often Vis expenditures even stuff like fixing Arcane Connections. Unlike the above, this one might be fixable by improving quality of said labs.
Gruagachan: Lacking MT, and fairly insular, the Gruagachan are unlikely to be aware of these limits at all.
Limit of Speech: It is simply not possible to work magic without verbal components - the louder the better! Furthermore, magic cannot affect anything beyond range of the caster's voice.
Limit of Blessings: The inability to bestow Give Blessing effects upon oneself without recourse to the use of Enchanted Tattoos is almost certainly a throwback to the tradition's faerie roots.
Limit of Resistance: Victims' ability to resist Gruagach magic with Stamina rolls and especially the Poetic Justice modifiers would seem to be another limit on the tradition's magic. Probably related to their role as judges.
Limit of the Gift: Gifted Folk Witches can learn Supernatural Abilities whereas unGifted ones must initiate.
Limit of the One Mistress: Covens that contain more than one Gifted Folk Witch are unstable (a consequence of the social penalty of the Gift, but might be interpreted as a limit by Folk Witches).
Limit of the Stars: Sabbats must be held on specific dates.
Limit of Curses: Curses require an Arcane Connection to the target.
Limit of Real Shapes: Shape-shifting requires a skin (or similar) of the target shape.
Limit of Vis and Healing: Healing requires vis expenditure.
Limit of the Animate: A dead character cannot be healed, and an unconcious character cannot be revived via Healing.
Limit of the Signature: Folk-Witch magic is indelibly marked in a way that identifies the caster.
Limit of the Church: It is hard/impossible to affect those who are on holy ground with magic (this is a consequence of the realm interaction table, but might be interpreted as a limit by the Folk Witches).
Limit of the True Companion: It is only possible to have a single familiar (at a time).
Limit of the Magus: It is hard/impossible to affect Hermetic magi with (Folk Witch) magic (a consequence of Parma Magica, but might be interpreted as a limit by Folk Witches).
Learned Magicians: Despite the lack of any real MT equivalent, most members of this tradition are well-educated and hence should possess at least some metaphysical understanding of how their powers work - moreso than say a gruagach or a vitkar.
Limit of Fortune: Tueor Fortunam effects' inability to aid their target against foes with MR almost certainly constitutes a flaw in the tradition's understanding of its magic - since it doesn't really make sense any other way.
Limit of Potency: It is impossible to create enchanted devices with permanent duration and/or unlimited uses. Devices that appear to do so are simply the result of extremely high Lab Totals combined with Lab Texts.
Limit of Specificity: Enchanted items must me fashioned with a specific target in mind and even then can only apply to improving a specific skill, healing a specific type of injury etc. This is probably a flaw in their theory.
Nightwalkers: Loosely affiliated, lacking MT, and having innumerable regional variants, the Nightwalkers are even less likely than other hedge magicians to develop a theoretical framework for their powers, but here are a few possibilities.
Limit of Straying: Magic cannot be performed while in the waking world.
Limit of the Seasons: Nightwalking can only be accomplished on the eve of a fertility battle.
Limit of Wards: No magical wards are capable of targeting phantastica.
Vitkir: These Norse rune wizards do possess an MT equivalent, but their magic is so different from Hermetic model that their findings are quite different from those of their Hermetic rivals. A few examples would be:
Limit of Runes: Continuous magical effects wrought with rune magic are terminated instantly if the runes themselves are destroyed.
Limit of Targets: Once cannot affect targets beyond about 10 paces unless you possess an Arcane Connection to the target in question.
Limit of Scripts: Despite the apparent simplicity of rune magic, it is simply not possible to perform rune magic spontaneously - All effects must be painstakingly researched by the vitkar if they are to hold any magical power at all.