I believe it would be tough to remove the seat, drop it to the floor and still have a finished look that would not hurt the re resale value. The RV would most likely have some wiring or water lines that would need rerouting as well. Possibly if you build a sturdy full shower pan step up that may make the access easier with some added height, or as a temporary solution add a portapotty in the trailer till your knee heals up, you also have the advantage of moving it outside to a private area if needed. It is great your still planning to get out and enjoy the outdoors, this should also help with the rehab and getting your mobility back. These washrooms are tight and challenging at the best of times, however don't let me hold you back be sure to post any mods or upgrades.