I'm curious about this as well and have researched it a little, a few things to think about
It will be a very cold shower pan if you don't insulate well under the bus.
Usually you want your gray water tank up as high as possible tucked under the skirt of the bus. If you have a shower lower than the top of the tank plus the required p trap curve youd have to position your tank maybe 6 or 8 inches below the bottom of the shower.
If these two things can be overcome and you have something sturdy enough to mount it to then I can't see any other problem with it.
Working on my bus now, I think I may have to bite the bullet and do a roof raise. I'm 6'4", thhe roof is currently 6'6" but I'm going to be adding at least 2 inches of insulation to the floor plus wood floors. And worse yet, my 12 year old will probably be taller than me in about 3 or 4 years. He already wears the same size shoe as me
. So I think I really need to figure the easiest way to roof raise which will make the shower pan in the floor less important.
Sent from my SM-G935V using Tapatalk