I agree that a cornuta deserves a killer viv. I'd like to have one myself.

If you really want to do this, I would suggest trying to tong feed him as much as possible and just keep him on 3 to 4 inches of small gravel covered in a 3 inch bed of sphagnum. Keep an eye out between feedings for BMs and remove them if possible. You could bury a pump in the gravel to move water around, dig out a small pool, and could also bury a media bag of charcoal somewhere handy to help with toxins (dang...I like that...just thought of it!). It's like an undergravel filter, sans everything but the gravel.

You could use stones to build walls, and terrace the plants in sphagnum beds above to keep him off your plants. My guess is that the frog will situate himself in a position facing the front of the tank, especially if you make a nice background. And if the sphagnum is deep enough, he may not even disturb the gravel.

These are just thoughts. I am sure the hygiene police will want to give me a ticket for callousness. However, natural environs do a lot towards the general health of our animals.