If airbenders get a wisdom bonus to AC, all benders should. Airbenders low defense bonus is balanced by the dodge, and there's nothing about the airbender that implies that they should have a second bonus to AC that any other bender wouldn't get. If we keep these armor proficiencies, we should probably drop the wisdom to AC option, unless we make it a level dependent thing, like gaining half the wisdom modifier to AC at say 4th level, and full sometime later.