It surely can be done.
But it would take a lot of work and money.
Keep in mind, all drains would have to be pitched.
Water supply lines might need to go under the floor, where they aren't heated, or easily drained over the winter, or accessed if you got a leak.
Venting the plumbing might take some doing. Trying to hide the vent, or make a new hole in the roof for the new vent.
A different shaped shower stall would be needed, and most likely a different shaped vanity.
Would you be moving the black tank. My tank sits on top of the floor with the toilet right above it. You would also have to move the drain valve.
You would have to move, and/or fabricate walls.
Also the problem of not adding too much weight
It might be easier quicker and cheaper to sell it and but what you want