I'm in the process of a complete overhaul to my 13' Scamp. Many upgrades, not the least of which is an outdoor shower.
When at most RV parks, it occurred to me that the curbside/entry-side is most "private" side, so I located my shower there, just below my "porch"
light. This location is on outside of the vertical cabinet inside, so the plumbing is hidden within the cabinet. I'm customizing the interior of the vertical cabinet so that I can have access to all the plumbing, while adding more efficient storage.
Obviously, the shower required cutting a hole into the shell. No big deal, IF you take MUCH care with your measuring and your cutting. I had no serious problems and the results are great.
Good luck.