How about a energy system based entirely on a 5hp gasoline engine, driving an alternator, something like a 3000 watt Honda GenSet. Exhaust to heat your water. Coolant air ducted to heat the inside of the trailer. Electric refrigerator
, range. You get the picture.
There could also be some cross-over, i.e., excess electricity generation could be diverted to an electric space heater when desired. A fluid cooled engine would be better. How about a marine outboard motor? It wouldn't be too hard to provide a closed cooling system with pressure tank that would use coils in the floor of the trailer as a radiator. When heat wasn't needed, the coolant could be circulated through a heat exchanger in the hot water tank, or just dumped via a small radiator and fan.
You see, the sky is the limit. Unfortunately for me this is all so unsettling, because in my mind is this war raging between cool complexities and the Keep It Simple, Stupid (KISS) philosophy. Normally KISS wins, big time. But occasionally it loses, and cool wins!!