If I wanted to create a ____-prodigy (wizard level power or more, with a single element only- the way harry has occasionally described in the books)... I'd take evocation... self-limited to a single element. With a willing GM, in return for that self-limitation, I could break pyramid on specialization (you already can just by having a wide variety of small, subtle foci- the difference at this point is flavor anyway- wanting something a bit more raw talent and less nifty toys).
Or alternately, sponsored magic might be more appropriate to someone like that. Sure, sure, there's no sponsor, technically, but flavor-wise, it fits better. Most of what Morty does is exactly thaumaturgy-at-the-speed-of-evo.