Manufacturers don't do torpedo heaters outside of campers because they are a PITA. You need to find a place for the fuel tank and the fuel receptacle, for the heater itself, and you need an exhaust that requires clearance. And for a heater integrated into regular airflow routing it gets even more complex.

Indeed - both heaters (torpedo and whatever the jeep had) blew hot air "around" and were not integrated into the vents. I think the jeep unit just drew from the gas can - not sure about the torpedo heater, but they were very economical for the amount of heat they produced.

-40 (air temperature - not windchill) is nothing to mess with. The instant heat from a battery pack is great if you're always close to charging, but there's absolutely no way I'd head into the wilderness in winter with just an EV.