I would think you could do a similar deal with a Mr Buddy outside the tent, running on propane, and the heat-powered fan would run as long as the propane holds out. I've used a Mr Buddy in my outdoor kitchen to warm an immediate area and have thought about making a plenum of sorts that is then ducted with a 12v fan to wherever I want, tent or van, etc.
I've run the Mr Buddy in my van's living space before for an hour or more before sleeping and it's quite amazing the difference it makes. I wouldn't hesitate to run it in my OZ tent, either, though they do create moisture in the air that will then condense on cooler surfaces. I wonder how it would be to move the warm air from a plenum, though, heated by the Mr Buddy heater. Wouldn't have to haul or collect as much firewood or tend to the heat source as often.