making clouds an aero surface wouldn't be a bad idea. most clouds/smoke surfaces don't actually count towards elemental affinity, as far as i can remember, but i could be wrong
also, you can rank each skill based on how easy it is to use with elemental affinity, with hydro being the easiest (water by itself is harmless, and even ice/cursed water/cursed ice don't hurt you as long as you stand still and don't try to run on them), poison/fire being harder since standing in them will actively damage you even if you don't move, and aero being the hardest since on top of taking damage they require more steps to set up. i think making clouds in general a "surface" for elemental affinity would be cool
