I didn't realize that cassette means that you have an outside door. I think we would have to use a porta potty as the camper would only be used for this trip, then resold. I think I would have to pick up a camper and then get a porta potty with the best height to adapt to the existing bathroom.
I'm quite leery of using a wood framed camper as we had a couple of problems with our old Hallmark on the rough roads in Mexico and SA is by most reports no better. We would be picking up both a truck and camper just for this trip. Truck either pre 2007 diesel(no 6.0 Ford) or gas and camper fairly small, our duramax dually and large, heavy Bigfoot aren't going down there, as we want more "back country" capability . Back country means off the major highways.