I like sponsored magic for any powerful focused practitioner, really. It is a great way to implement the "hot headed pyromancer" and similar element based tropes. It is the same price as channeling + ritual, so there isn't really any difference there, but it emphasizes the specific element a bit more than just the skill. It is the difference between "I know fire magic" and "I am fire magic", which is an interesting thing to play, I think. Kind of an extreme version of Becq's idea, I think. It might not fit every character concept, I admit, but there are a lot of ways around that.
There are a lot of ways to power up a focused practitioner, sponsored magic is only one of them. The most important rule for me is: only because it looks like magic, doesn't mean it needs to be magic.
What do I mean by that? A lot of the powers listed can be emulated with magic, and more importantly, they can be used to emulate the increased knowledge in a part of your magic. An aquamancer? Take the aquatic power. An aeromancer? Wings, here you go. A pyromancer? Breath weapons and you can sling those fireballs like it's nothing. Using earth magic to bolster your strength when beating some monster up? Why not take inhuman strength?
The mechanics only have to be loosely connected to what happens in the game. And you can interpret the powers any way you like, as long as you pay for it.