So, we've seen the caravan trailer. It's amazing. I would love it if one of the more talented members of the community could make a drivable, 4-wheeled version that we could bang up without having to attach it to some car.
http://www.beamng.com/resources/etk-6000-4000-series.1343/ It's not a motorhome in the sense of being able to walk from the cab to the back, but its got a sleeping area, plus it's powerful. I think the side opens too