No need to tinker with the AC and some kind of fan mod. If you don't want the AC, just take it out and put a patch in the roof and close up the hole. That would reduce the potential for water intrusion. If you don't already have a roof fan, put in a good low-power-consumption Fantastic Fan.
Just turn the water heater on when you need it. It only takes about 15 mins to heat up, or less if the water is already fairly warm.
The heater is a good mod, uses less propane and zero electricity. You do have to be careful and keep the dust off them, however.
Your best mod for boondocking is a solar system plus a good battery bank.
Single empty-nester in Middle TN, sometimes with a friend or grandchild on board