Fire place idea, does & doesn't work, depends on where your tanks are located. I had my house up to 75 last night, but can't keep fire going all night. Even w/house at 75 tanks were still dropping to just below, then once fire goes out, down they go. But lighting another one first thing in the a.m. would at least keep them around 68 -70. Unfortunately for me, I have 4 tanks inside and 8 in the garage. I think I need to install a wood stove out there.
As for the trailer idea, good call. My trailer does not have one, but I bet some people don't think about that. And 50 amps could actually run the whole house. Minus the stove, dryer, DW. As for lights and power, 50 amps is plenty. Good call..