I may be throwing a rock in the pond here... And I'm not saying I have any definite answers
But...
Familliars can learn and cast spells....
Also:
As for the speaking and hand gestures....
I would definitely lean toward the premise that the words spoken and the specialized gestures do not do much magically on their own. The vocal and physical elements of Magic, in my mind at least, are instruments to focus the powers of the mind.
Thus in human form, Vocalization, and hand gestures play a great part in magic, but in animal form the same thing would be accomplished quite differently, and it would be based on the form of the animal, how it moves and navigates, and how it relates to others of it's own species.
Yes, I'm implying a learning curve for the caster... I think that's only fair to the system and in keeping proper balance. But I would love to see that Lightning Eagle!