OK, next I messed around with some foam core to start mocking up my floor puzzle more exactly. It took several iterations, but I eventually came up with something I think will work and be robust enough for play.
The room will actually be on a 10x10 inch platform, but the outermost squares will be unplayable since the slanted ceiling will be leaning over them too sharply. (The room will be a square-based pyramid with steeply sloped walls.)
Here is my original idea for what the floor of the room would look like to the players. The circles sketch in where the rotating statues will go. I have two designs for the moving floor section, a simple square and a more intricate stepped shape. I am leaning toward the stepped shape. I think it looks more interesting and I think it will surprise the players more when it moves.
Here is a view of the underside of the puzzle floor. This is a view of the cover plate that will hide and protect the workings.
With the cover plate removed, we can see the bottommost part of the sandwich of layers that form the moving floor piece. The notches cut out of each side are for the four small locking pins that will be controlled by rotating the four smaller statues in the corners. Here you can see how I will use LEGO Technic gear pieces to move the pins in and out. (I only put down one set of gears to show where they will go, but the final version will have gears for all four statues/locks.)
The idea is to have the four smaller statues facing away from the central large statue. Turning each smaller statue a half turn so that it faces the central statue will fully remove the associated pins from the notches, making it possible for the floor piece to slide.
Removing the bottom part of the sliding floor panel, we can see the gear attached to the large statue and the cutouts in the fixed floor. The purple blocks are actually attached to underside of the sliding floor panel while the pink outlines help show the edges of the slots cut into the fixed floor. The toothed track pieces will be glued to the fixed floor. When the main large statue is turned, the gear attached to it will pull the sliding floor piece along the track, exposing the hole.
And here are the same views with the LEGO pieces removed to make it easier to see the foam.
And here are views of the individual layer pieces themselves from bottom to top.
Skipping over the simple bottom cover plate, here is the notched piece that receives the four locking pins.
Here is the fixed floor with the holes cut out. With and without LEGO gear track pieces.
And here is the underside of the sliding floor piece, with and without the LEGO gear.
And here you can better see the tab pieces that fit into the slots below.
All right. Next step is to start making this all up in real materials. The thickness of the LEGO Technic gears will be a bit of a challenge since they are thicker than the standard luan plywood I tend to use for floors.
It's also going to be a challenge getting the friction between all the elements just right.
Good luck everyone! I look forward to seeing all your projects come together.