He's installed a wood stove! I don't know the benefits/downsides vs propane, but it's definitely cool.
For the Rialta, the first thing I'd do is build removable insulation for the windows and research replacing them. The bed having windows on 3 sides is a definite winter time bottle neck. The next is look into a fluted catalytic heater to reduce interior moisture. I don't think I'd want to go wood.
He's considering a thermoelectric generator which got me thinking about a propane run TEG. I found a reasonable sized one (with no list price) at http://www.redhawkenergy.net/globalteg.html
email@example.com/day doesn't feel very efficient to me.