Know What Class I Wish For? Geomancer
Think about it; it's spells could change based on the area it's in. (I would say 'weather' but that would be annoying)
Give it a quick-cast 'stance' to reverse the elements it casts (IE: Fighting Titan? Stance into Reversing your spells and now everything you cast has an Aero-flavor!)
Plus, you can micro-manage based on the battlefield:
Standing on poison ground? Your spells now poison! (But still have the overall element-theme of the area)
The ground slows? Now so do your spells!
Give the Geomancer a way to mitigate painful DoT ground-effects in boss fights to power up his spells!
Or even some sort of elemental focus skill:
Cast this, and take on the Aspect of the surrounding Aether (IE: The element most prevalent), and it even changes how the Geomancer looks for the duration.
(He looks more earth-like and sturdy for earth, or his clothing becomes more wispy and flowing for wind, etc)
And that would feed into Reversing the element for boss fights; draw in the element, then reverse it, then start casting spells!
I dunno..I just think it'd be fun to have a class who's spells are themed based on where he is, and gain the effects of what he stands on.