I spent a happy day playing with my dioramas and bikini car wash. I even got in a couple of hours riding mine cars in Tomb Raider!
Here are the finished diorama bases:
They fit in the upper level quite well but are quite high (4 inches):
The problem comes when you want to get them out of the layout to swap them over. They will only just get out and I’m not sure a mill will fit too. I’ll make that section of the fascia easy to remove.