Yeah, I'm struggling with the same thing. In my research, there are a couple options for coach air that can run while parked:
1. Those with pony motors (usually small kubota or yanmar diesels) running the compressors. Can add an alternator to charge house batteries and run the bus off inverter 24/7. They can run the AC all the time as long as you don't have a NO GENERATOR rule in camp. No way to run these from shore power. They probably weigh 1,000 lbs all-in. The engines are built to last, but the freon lines are prone to leaking and a nightmare to fix.
2. Those that are all electric and normally run from 500 amp engine alternators. Too new and expensive to be an option on any skoolie I can afford, so I haven't looked further than that.
Best option I have found for lots of BTU/dollar in a "professional" looking install is a 240v generator and a multi-room mini split heat pump. They can also run from a 50 amp RV hookup (but not a 30). Big problem is mounting the outdoor unit somewhere. I would probably mount it inside in the back of a closet or cabinet and vent. Similar to this guy: http://overthetopcargotrailer.blogspot. ... egree.html
If you need to limit yourself to 120v only (like I do) then you spend more money on separate mini splits (and find space to hide multiple compressor units) or go to windowshakers and figure out hard start capacitors to get them to run on extension cords and small inverters or generators.
After the research, I see why buses with air always bring so much more. There isn't a cheap solution to cover everything.