Steve...
I don't know about a quick way to get at the water pump. The way I have the set up now I would need to remove 6 sheet metal screws and two bolts plus disconnect two hoses to get back there and that would only take a few minutes.
We also have a adjustable regulator, Watts N55G or somethig like that. I have a heat taped water hose we use when the weather is cold enough to freeze. There is plenty of heat tape at the end to wrap around the spigot and regulator. I think if we were fulltiming or in cold weather a lot we might look at a setup like you suggested.
We got the shower-black tank idea from our dealer when we bought the trailer. Works great for the most part. I didn't realize other people had done it also. Ours is also on a quick disconnect in case I need to spray the wife on a hot day.
