Champion concept: Elemental mage

Well, i've been thinking lately, we have mages, earth/plant mages (Taliyah, Zyra) fire mages (annie, brand) Air users (janna, yasuo) and water users (Nami) why cant we have a mage that mixes all elements into 1 champ.

The interesting concept about this is what about REALLY mixing the elements, i mean, pick 3 diferent elements for Q,W and E, and R will trigger the effect of the chosen skill. for example, if we put a fire skill in Q, press Q+R and you get to trigger a fire attack. BUT if you pres Q (fire) + W (lets say earth) and you activate the R, you get a lava skill!!! or wind + fire you get a fire tornado. Imagine that. Also, if you trigger 2 times the same element you get a stronger attack! (but with a highly extra mana cost).

What do you guys think about it?