As an alternative to a two stage furnace, I wonder about a vented Platinum Cat system. The fan it uses is a lot smaller and takes less energy than the fans forcing air through the RV furnace's heat exchanger.
If I had to reduce my must-haves from my relatively long list to a few, it would be a fiberglass or metal roof, Azdel sides, E-450/V10 chassis, and an onboard genset.
One thing I'm curious about... are heat pumps that better than a conventional A/C unit with a heat strip? Below 40 degrees, heat pumps stop working, but a heat strip may not be as effective as a Vornado space heater (or similar), but would definitely help supplement the furnace.
