Your last drawing does look quite workable.
I might add some low point drains to the pressure side, which would be a big help in winterizing (particularly if you blow the lines out vs. pumping antifreeze), as well as being handy when needing to do repairs or maintenance on the plumbing. I'm not convinced they're absolutely essential, though. Virtually all RVs do have some sort of low point drain system.
If the crossover from the left to the right side of the van is overhead, there presumably should be hot and cold low point drain in the sink/water heater area, and a cold water one somewhere near the pump/city water inlet. The shower could serve as the low point on the driver's side of the hot water line with a tiny bit of care. If the crossover is under or in the floor, then the low point would presumably be somewhere in that general area.
I've thought about adding a hose spigot to my RV, but have not done so yet. It seems it could be handy, but I'm somewhat concerned with having another thing sticking out to get in the way of trees etc. and with arranging for cold-weather safety. (An interior shut-off back from the spigot, or a winter/freeze-proof sillcock where the actual valve is some ways back from the handle would be good approaches to avoiding winter damage.) In your design, you might be able to have a hose tap near the water heater next to the side door and avoid a lot of these concerns. But, of course, that is all very much an optional bit of equipment in any case.