Hi, I have a similar set up, except I don't have an FB unit.
I carry both a propane powered Yamaha 1000 generator when boondocking:
Yamaha Propane and Natural Gas Generators
Any carry 3-4 bikes on the roof of the burb with Yakima's King Cobra mounts:
Though you can camp in an Airstream in the winter, make sure you're LP tanks are full. Airstreams do have insulation, but as any streamer that has a newer one can tell you, they are not exactly air tight, meaning your furnace will run regularly. If that is not an issue, then, sure, the heat from the furnace should keep the pipes from freezing, and the tanks are duct heated from the furnace.