You wouldn't have to tap the propane line under the stove. In the 25' FB it goes behind the drawers to the right of the stove. Getting a line to the outside of the cabinet would be a challenge if you wanted to come out in front of the cabinet, but underneath the cabinet drawer under the sink if you have the older double sink could work.
The roofs have been white for some time to reflect heat in the summer. They must reflect heat in the winter too, though, as has been said, the poor insulation and all the windows make Airstreams not the best for cold weather camping anyway. Whether the aluminum exterior, shiny or not, reflects heat, I would think so since plumbers often use aluminum sheeting to reflect heat away from flammable things when soldering copper pipe in the walls of a building. Arctic Fox is known for cold weather use (or Desert Fox for the reverse), and they have some nice floor plans, but decor is old fashioned.
A correction—the fiberglass batts are 2". They are hardly enough to provide much R value. Studies show fiberglass batts generally are installed poorly and their actual R value is somewhat less than what it says on the batt. Once they get wet from leaks, they may get worse as they can clump—that further reduces their insulating capabilities.