I've gone with the wet bath approach in mine
. I put down a 30x60 shower base and mounted the toilet in one corner. The thought is the toilet consumes some of the floor area, but it's short so there's still plenty of elbow room for washing oneself. Anyway, all the high-end places have a bench in the shower, right? So much the better to be able to attend all those bodily needs at the same place and time..?
I still haven't really lived with this setup in a finished form; we've used it just a few times with black plastic sheeting surround instead of a real hard-wall enclosure. Still need to figure out how I'll keep the towel and clothes, and especially the toilet paper, dry through showers!
Maybe build yourself a custom pan with stone or tile and the rubber sheet shower pan liner stuff, like Offgr1d did in hers
. Or build the pan with fiberglass. Put the throne up high over the wheel well, since you don't need so much head room while sitting anyway, and the shower drain down low there behind the dinette.