I considered this as well when installing a water tank in my wildernest. I came to the conclusion that while it would definitely work, the extra weight and cost of a pressurizable water tank and plumbing and a regulator, far outweighed the cost of a RV water tank (~$40) and an electric water pump (~$30). Even with already having 5 gallon pressure vessels on hand (Corny Kegs) it seemed fairly inefficient as unless you happen to have a round hole, a cylindrical tank stores about 30% less water than a square tank.
On the other hand if you have a CO2 tank for filling tires, you could have carbonated water with this system! Add some flavour syrups and you have a mobile soda fountain.