There are plumbing codes that apply to RVs, but they don't in any way prohibit using the same outside bay for various connections, both fresh and black/gray. There are requirements for things like vacuum breakers or other backflow prevention devices, the height of sink taps above the flood level of the basin, etc.
I'm afraid I don't see what's so disgusting about having both fresh and waste connections in the same bay. They aren't connected to each other. In my house, the pipe in from the well and the pipe out to the septic system both go through the foundation in the same general area, too, and any servicing or whatever needed to them would take place in the same corner of the laundry room, next to the pressure tank and water heater.
