I do sort-of like that idea for the "magey" type. However, to keep with lore, it would have to be earth, fire, water and air. Many physicists will argue that this was the early expression for the 4 states of matter: solid, liquid, gas and plasma. Under this philosophy, "ice" would fall under "earth" (because it's solid), but the idea is that we want to express the extremes of temperature and perhaps air can do that sufficiently? (blast them with cold air?) Just a thought.