I do like the premise, but are you familiar with dungeons and dragon's magical system? http://en.wikipedia.org/wiki/Magic_of_Dungeons_%26_Dragons there are eight classes, each pertaining to one area of magic. I think theres a game called ~aprentis that focuses on pure elemental-based magic... so using that system could definitely set them apart. Not to mention, those eight classes cover everything from necromancy to illusions, shapeshifting, healing, etc. :)