The thing is, you doln`t want to be casting your monster turn 5 , you want to be casting it turn 4. It`s simple Maths, an Air Elemental has to swing for 4 for four turns to overcome the damage advantage that the Troublesome has by coming down a turn earlier and so getting another attack. By that time the game is over.
Add in that the deck want`s to be able to suck up it`s Islands to Gush ASAP and the Air Elemental is plain inferior. Extravagant Spirit can be added, but has no synergy with Gush or Thwart, you`d maybe add Elementals for the mirror, but I doubt it.
Gush is the real reason that SKies is very good, as it`s pure card advantage and fuels all your ACC spells (although you really need to choose if you prefer Gush or Thwart, as they kind of work at cross purposes to each other - run 4 of one, 2 of the other).