I love reading old threads like that one, back when the Leaf was just a young pup!
One of the posts linked a cool little device made by Coleman, a propane heater that fit in the cup holder
I was also intrigued by a Rube Goldberg Igloo A/C unit
lots of goodies in that 6 page thread. I like how one guy suggested a much more efficient heat pump for our Leafs, only to have someone else point out while it may be more efficient in less cold conditions, in the bitter cold it wouldn't work very well(how true that is).
Oh the issue that immediately came to my mind with the Coleman propane heater(non vented) is all the moisture it would add to the air in the cabin, it would be basically worthless in the cold if you didn't want moisture/frost or ice all over your windshield. After all basically burning 1lb of fuel would result in ~ 1lb of water all over your windshield and other windows, not good at all