Have seen scamps with front couch/bunk option where they:
- Put a porta potty under the couch in the center storage cabinet, slide out for use. Still have couch and upper bunk.
- Build custom seats to replace couch. With porta potty going under/inside seat by the door. Seat top flips up for access and becomes back rest for potty.
Both of these allow you to keep front bunk functional.
The second option can be done as part of turning the front couch into a small dinette by putting custom built seats on both sides and drop table in the middle. Mini version of the back dinette with place for potty in one seat.
You could however not easily use the potty if it is stowed in a custom seat while someone is sleeping on the dinette/bed or the bunk above it. So you would have to move it out for the night if your goal was to avoid night trips to the bathroom.
Option #1 does allow sliding the toilet out in front of the couch/bunk and using while those beds are in use. Essentially it only requires purchase of porta potty that will fit through center cabinet door under couch.
All of this is Scamp
specific but at least a couple of other campers have much the same layout so the same approach would work.