It's not the freshwater head I object to, it's the need to
make freshwater for the head. As I said, if you have surplus freshwater from a raincatcher or a watermaker or the fact that you've got the complimentary tap at the Port Captain's personal dock, that's great. I would also say that even an occasional fresh water flush (or a vinegar flush or some other kind of "treatment") is going to do any shipboard plumbing a world of good by killing critters in the works.
But the thread of useability grows thin indeed if this is the case in my view, particularly if you have the usual flat bottomed hull and maybe 50 gallons of water tankage to play with, and if you have to have a series of electrical
pumps to make it work. I have 200 gallons of water tankage, and if I throw a small watermaker in there, I might be one of "those guys" who can use a diverter valve to have a freshwater head, if only to cycle through "older" water in designated tanks.
Everything on our boat, with the exception of certain navigational and communications gear, is moving in the opposite direction of this particular example of modern comfortable cruising. I
have pressure water, but I am going to a second set of taps for foot-
pump water. I
have a wired hot water heater, but I am plumbing it into the heat exchanger so that we will have "bath day" on "motoring day". I
have A/C, but because the amperage to start it exceeds what I can make with
inverter and Honda 2000 (well, it
might kick, but that remains to be seen), I will generally not use it. The
windlass is manual first, with electric backup, and so on. A huge Patay manual bilge pump has its pickup lower than the electrical Rule bilge pump, and so on.
All this isn't a Luddite impulse, but an attempt to have more than one way to accomplish onboard tasks, particularly ones that involve electricity. The reason for this is that
without exception, cruising narratives and boat delivery stories tell of the gadgets that didn't work due to lack of robustness in design, the harshness of the saltwater environment, or because the wiring was just too damn complex to service in a pitching boat.
If it is a matter of throwing a few switches and turning a few valves to turn our passagemaker from a muscle-operated workshop to a gently humming den when the appropriate power and water manifest at a dock, why wouldn't we? It seems quite strongly to me that I can avoid a world of maintenance hurt thereby at very little "inconvenience".