Anything is do-able, if you throw enough money at it, but this is one of those things that may not be worth the effort. Unless you are a "Little Person", you won't have any room, and you would be giving up additional space, which you don't have much of....and then, there is the plumbing issues, since the shower would have to drain into the gray-water tank.
It might be smarter to invest a bit more into a really nice outside enclosure for the outside shower, since you already have that.
Of course, there is probably someone who has made this conversion, so maybe you'll get lucky, and they can give you some advice.
Good Luck:)
Bill & Claudia / DD Jenn / DS Chris / GS MJDogs: Sophie, Abby, Brandy, Kahlie, Annie, Maggie, Tugger & Beau 🙂RIP: Cookie, Foxy & Gidget @ Rainbow Bridge.😞2000 Winnebago "Minnie" 31C, Ford V-10
Purchased April 2008:B FMCA# F407293
The Pets