Started on the rear floor today. It seems doable but it will take some sweat. The rust has especially hit around the mount points for the seats. Whoever put in the camper interior did not bother to seal the holes. I intend to fix this.
The first part of the repair is the cleanup of years of gunk and rust on the floor. Some purple degreaser and a bunch of shop towels is the answer. Having a shop vac, water bucket and brass brushes makes the job more efficient.
One bit of good news is the worst rust is on the outside of the vehicle so getting under it is easier. Creating a patch out of sheet steel is doable but will be a challenge. Preliminary plan is to rivet it on but plans may change.