Awesome idea and great looking product!
I actually have seen this before, many years ago, but it went down al the way to the ground and it was scratchbuilt especially for a convention scenario. Yours looks much more manageable and useable, even for casual games.
How deep does the terrain go?
I've got modules with different types of terrain (3 of each, desert, snow, temperate, wasteland, each 120x60cm) that I put together to create a full table. They're also 34mm thick; a foam sheet plus a sheet of MDF on the bottom; would your solution work with that limited depth?