Mostly Harmless, that Jerven bag looks interesting. Thanks for posting it.

Bacpacjac, we used to do something similar with a military poncho and poncho liner and sterno, while sitting on a rucksack. You just had to leave an opening in the bottom for ventilation and keep a seal around your neck. The candle may be safer, though with less heat. You could get warm and dry very quickly with that setup. I would still be cognizant of carbon monoxide though. Keeping you face out is important. The tea light would be easy to use and to carry.