Well, from what I've seen, most people immediately get taken in on sponsored magic by the thaumaturgy at the speed of evocation. At first you think its easily one of the most powerful, easily abusable powers in the setting. Then you realize, wait... What exactly CAN I do with this?
The answer, while potentially being still as broad as thaumaturgy normally would be, is significantly less potent. For the most part, you just have to be clever and quick on your feet to get the most use of it. Drachasor actually mentioned a lot of the ideas I'd thought of before to try to make use of it, as well as some I quite hadn't yet. I'm very surprised, or I guess actually I'm not really, that you dismissed so many of his ideas.
But it comes right down to the idea, that thaumaturgy isn't really that useful for direct combat, at the speed of evocation or otherwise. Any effects that would cause direct damage against your opponents would most likely be better off being a simple evocation blast. The best benefits you could get, are ways to indirectly effect the combat, and better arrange things for you and your party to succeed... But what YOU are looking for, I'm sorry, but these are not the droids you are looking for ;P It just isn't... So if you chose Sponsored Magic for Thaum at the speed of Evo, I'm sorry... You need to start looking at other advantages to having a sponsor. Because what a sponsor really does, is really a whole lot more >.<