If they ever choose it has to be the ark as we all know but darn I will admit even if they released it on April 1st for fun I would buy a car wash of doom playset
Would love to have a Decepticon underwater base set. With working elevator going up the tower for Megs and company to enter/leave by.
Personally, I think an Autobot City/Lookout Mountain set would be amazing. It'd have to have the rocket launcher bay, the turret Devastator destroyed, the medical bay, and the level Prime and Megatron fought on (complete with a dropoff).
What about unicrons head for cyclonus and the sweeps where they retrace galvatrons last fight (five faces of darkness)