Um... that looks a tad too heavy for my poor jeep to tow. Neat idea for a hunting shack or something like that though.
ETA: Something I have considered is using the water pump, the hot water heater, and the 19 gallon water tank as a thermal mass. Recirculate the tank through the pump and into the hot water heater and back into the tank, bringing the whole tank up to 100+ degrees F. That would warm the floor since the tank is between the wheels, and warm the interior, and protect the tank from freezing. But I think the way I built the floor has too much insulation between the tank and the interior for that to be effective, more of the heat would bleed to the outdoors than into the trailer.