Other than the mounts for the toilet base (the ones I've dealt with we're bolted to the floor on a wax ring), it's probably doable. Using a low flow toilet, 1.6 gallon/flush, you'll get about 20 visits to the throne before the sanitation engineer has to dump the tank. Unless your sinks are strangely plumbed into the black tank, I don't see why you would have to worry about that.