Hi Marcus,
If you don't mind me making a suggestion or two, I think the basic idea is sound. However, it might be as well to simplify it as much as possible; have, say, two frames with one screw each, and use something like 6" x 2" beams longitudinally, and 3" x 3" beams transversely to spread the load. The bottom platten would need some support under it similar to the beams applying loads to the top platten, or it would just sag between clamp frames. Using two screws per frame, and multiple frames, seems just a complicated way of doing something a dozen or so F-clamps could do.
The square frames could be 4" x 4" mortice and tennoned at the corners, with a long proprietry vice screw to apply the load. Would be fun to build, but obtaining all the packing and making sure it was all square and true would be a bit slow. Storing it all might take some space, too. Worth it if it's something you'd use a lot, but for just a few, maybe two plattens, one on the floor, job between, platten on top and pile lots of bricks and rocks on it might be easier and cheaper.