You should still be able to do the quests for TP and cash them in. But what if you got one every time a trainable spell is available without having to buy all the preceding ones? For example this is what I, a Balance Grand, (Hopefully a Legendary soon) would do.
I think it's a great idea, especially for the Astral schools and hidden trainers in Celestia. To my knowledge the max extra tp's you get are 6, and having to buy consecutive spells are a waste of tp's, especially the morphing spells, I mean I'm a Level 60 Life Wizard, why on earth would I need to morph into a Life Treant, who has less life then I do, a mander and the gobbler are all pretty useless in Celestia anyway. The Storm Cat, Draconian are good in Celestia, but you have to spend 3 tp's in order to get them.