What would be even cooler would be more essential cargo attached to a movable tray, beneath the camper. 2 batteries, 2 propanes, jack, the spare tire, generator.. all on a movable slide supported by two tracks inside the frame rails, and a big lead screw that moves it as far forward as under the tongue deck (also for access), and as far back as right next to the axle. Probably 200 pounds of stuff you wanted to carry anyway. So instead of a pump with 2 tanks of water, it's just a motor turning a threaded shaft.. and you could have some type of auto/manual/off switch to control the thing.
edit: you could also do a second tray behind the axle, tied into the same motion. it hits the forward limit with the forward tray is under the deck, and its rear limit is against the back bumper, when the forward tray hits the axle. I wonder if 3' of movement is enough to get the adjustment you want, that's likely the limit here.