The building, the ride system and all the show doors, mechanical effects, lighting/projection systems would be the be expense. It should be designed so that artists, working mainly digitally, could easily and quickly change anything. It wouldn't take that much time or cost to paint some 2-D flats here and there to add dimension. Nothing added later would have to be designed as permanent; just slide the pieces into the existing permanent frames and stands.
And, heck, I bet Garner Holt could design a couple of AA's with easily-swappable faces and body parts.
But, frankly, I'm not expecting any AAs on this.