Interesting that Elementalists have no reveal capability.
To keep with the lore, how about when attuning to Air, lightning is called down onto the player and grants a wave that ripples outwards and breaks stealth to enemies within a XXX radius.
The cooldown will be around the X sec cooldown time for attunement swapping.
Obviously the cooldown timer should be realistic such that FA builds don't abuse it.
I'm thinking 9seconds, with reveal of 3seconds?