It's just a box camera isn't it?

You don't really need a ground glass for viewing. If it's got basically fixed focus then you can go much simpler.

If you really want to focuss then you can just nest two boxes together. You did say weight doesn't matter-) You can even add tilt by adding a third box to the front. Or a fourth to the rear for rear tilt. The tilt boxes are really lids. Use indirect rise. You can add shift by designing a shifting lensboard. Basically the lensboard is mounted on pegs to the front box. Not exactly the quickest way to work but simple.

Instead of normal film holders I was thinking removable back. Take the back off. Replace it with a film holder back. This could be a simple book type film holder. No ANSI standards for this anyways.

I've had a similar idea for shooting colour paper or film. But it's going to out wiegh a hummer.

One more thing. Everything old is new again. If you have "View Camera Technique" by Stroebel then check out the chapter on the evolution of view cameras. Mine includes a drawing of a box camera with multiple boxes.