My basic idea is a "T" in the under bumper compartment allowing me to connect to shore water from both sides. I'd also like to plumb in the fittings to run an outdoor shower (hot/cold). I could route the water feed line into the coach under the bed and have plenty of room for a pressure reducing valve/backflow preventer. I could also plumb in a bypass to allow draining the system. I'd like to minimize the number of holes I punch in the floor as well.
I understand the concern about freezing problems. There's no way around having water on both sides of the coach (galley and head). With the right valve set up, I could shut a valve inside the coach and open both ends of the "T" to allow any water in pipes outside the coach to drain. As for inside, I guess it behooves me to keep the lines empty or the coach above 32 degrees.