My off-road POPUP has the cassette pottie/shower combo unit...
They pretty neat to have but we have probably only used the sit down shower maybe a couple of times over the last five years... The pull out cassette holds 6 gallons of waste and you just pull it out and roll it to the rest room and pour down their toilet. Does not smell inside trailer at all.
If I was to install one of these I would just get the cassette pottie version only. Doesn't take up as much room and is totally self-contained. The cassette door is on the inside of the trailer in this version shown here. Same deal just pull it out and roll it to the bath house and pour down their toilet. With the top lid down this just becomes another seat or storage area on top.
Roy Ken