In Hooks we have a magus character who has a familiar without any magical might. The core book says that a familiar must have inherent magic. This familiar has something akin to a supernatural virtue. This implicitly answers the question of whether or not a familiar must have might.
Such might-less familiars have the opportunity to learn at the same rate as humans, avoiding the might penalty to experience gain from RoP: Magic entirely.
Because familairs will likely have few other responsibilities to distract them, I imagine that over the course of the order's history there have been at least a few familiars who have studied magic theory a great deal, probably more than even dedicated magi (they have no magical arts to spend their time with, they aren't needed in the lab all of the time).
So it seems to me that there is at least the possibility that some of the greatest tomes on magic theory that the order has were authored by animals.
I'd challenge you to come up with a tome and a corresponding author for some of the greatest magic theory summae (?) that have ever existed. What sort of a familiar wrote it, how the book reflects their unique perspective, what was it about their personality that made them such a great authority, and so on.