I think this idea sounds awesome and similar to what I was thinking. For Destruction I was thinking something like 5 basic elements like Water, Wind, Fire, Earth and Lightning. And then you can mix elements to create a new one. Like Water in one hand and Wind in the other dual casted to create Ice or something.
I also like that idea but wind, water, and earth have never been in the lore. They would need some major magical event to happen to randomly include those into this game.
Well.... actually, lore has never stopped them from taking stuff out.