Idea: An airship 'dungeon'
All the way through 2.0, I was hoping there was going to be a dungeon based on board one of the Garlean airships (like the one that was destroyed over Silvertear Lake), I absolutely loved the idea of fighting on a moving airship in the sky. Perhaps a battle could take place on the roof of the airship, with players having to watch out for sudden movements of the ship, or strong gusts of wind. I loved the airship part of XII, so something along the lines of that would be really fun to play. :D