I'm thinking that for evocation, this would give him effectively Wood and Spirit as elements, and for thaumaturgy (possibly at evo speeds), illusions, veils, and biomancy. I'm not sure if that's too broad, too narrow, or just right. Also, most sponsored magics seem to have some additional minor benefit (+1 to power for a certain type of magic, weakening enemy faction's toughness powers, etc.), and I'm really not sure what would be suitable here.
Any input, guys?
Strictly speaking, the element / specialty would be his sponsor's Purpose. That can be both more an less limiting than splitting it up into the elements / specialties you're discussing. But remember (GS spoiler): You can do wards, attacks, divination, and a lot more with "just" an Ectomancy specialization.
In any case, the Wikipedia article on Reynard the Fox suggests he was a "peasant hero character" whose targets were typically clergy and nobility (the powers of the times). I'd suggest making that your purpose. Wrap it up in an aspect and you'll also have your element / specialty. Something like "Fool the Powerful" or whatever fits your concept.