The problem with living in South Florida is that it's next to IMPOSSIBLE to really go into the backwoods anyway, without a really long drive.
My potable water will be in small bottles in a separate cooler anyway--if I can squeeze a few bottles in for the wife and kids. (Most of that space will be devoted to my beer.) The tap water is TERRIBLE in this neck of the woods, all of the way down to the Keys, and everyone drinks bottled anyway.
I envision using the faucet and sink more for washing up, brushing teeth, cleaning dishes, etc. I could probably screw a hose to a campground water supply and fill it up like that. (Pretty standard fitting.) Or just bring a case or two of water and use a manual marine bilge pump to fill the tank.
Heck, I was even going to consider eliminating the ice box, because those items can be kept in a separate cooler. It just seems like a nice convenience to have it there right near the range/stove and microwave.
I haven't given much thought to galley design yet (I have so much to go). But this thread interested me because it got me thinking NOW about this. As a matter of fact, if I give some more thought to this gravity-fed system, maybe I can run the same water supply to the side of the TD for a shower.