All depends on how you want to play it. The way I happen to like to visualize shapeshifting is sort of based on the Riddle Master of Hed books; the idea that you have to know/understand an animal to shift into it.
I think the sponsored magic might be along the lines of the way I would go, with maybe an aspect required for each shape 'known' and a FATE point for each transformation (both ways, which could be interesting when the PC is running low).