Just a little food for thought...
I've kicked around the idea of using a lantern and replacing the cylindrical pyrex globe with a piece of sched 40 aluminum pipe to form a brutally efficient heater. Greenhouses use pyrex 'cool tubes' around halide lamps to keep the heat off the plants:one of these slipped over the lantern assembly to serve as a duct would yield a pretty effective double walled heat exchanger. a PC fan pushing cabin air from the cold side would give you loads of potential airflow and the seal on the aluminum tube could be made with lagging (wood stove door gasket). All that remains is to figure out a way to duct in combustion air without letting exhaust gases into the cabin.
Has anyone tried using those Coleman tabletop propane water heaters as part of a hydronic system ?
Seems to me that one could plumb it into the trailer's bottle to serve both heating and hot water.
FYI regarding the Cozy Cabin heaters: personally, I'd go for a Force 10 or a Dickinson instead. Parts are WAY easier to find wherever you might be camping. I just replaced a Force 10 with an Espar and I'll probably credit the boat's owner a bit on the bill and keep the old F10 for my own build. I would be sure to factor the cost of a CO monitor into the job as well.