I would really look into HYDRONIC systems for heat. Use a field of water lines laying in the sun to heat up a large tank of water all the time - then pipe that thru your trailer hot water heat exchangers for heat. SMKETTNER is doing this now routing his hot water tank around his other tanks to keep them from freezing. Not sure how you could miniaturize the water line field to fit on top of the trailer ??? Backup heat for the water tank would be propane... You can also use your MH engine to heat up your hydronic water tank as well when necessary... Maybe several mirrors on the roof of the trailer tracking the sun and positioned on a central pod of some sort to use the sun rays to heat water at a point. The big idea here is to always have a source of hot water heated by the sun somehow...
Moving hot water pumped thru lines around your other tanks will keep them from freezing as well... There are all kinds of hot water radiators available every now - even floor tiles with hot water lines built into them...
Going in the opposite direction one of my friends that lives in ALA routes his water down into the earth and has found where he can have an unlimited source of 78 degree water to use - just pumps it thru his heat exchangers in his house. He lives by a LAKE and I think he has experimented with using the Lake Water from the bottom of the Lake to do the same thing. What ever temp he gets is very stable temperature wise coming from the bottom of the Lake the year around..
I have seen several roofs setup for something like this on houses but making all of this fit a trailer roof my not be impossible to do.
Solar panels for keeping batteries charged up which you are already doing...
Look what they do with hot water in the desert country of AZ for making lots of AC POWER using the mirrors farms.
Roy Ken