I don't understand these arguments at all...
If you have a LiFePo4 battery and camp in extreme cold weather, move the battery to inside the camper. Problem solved... Unless you are sleeping with a camper below -20 deg, the battery will be plenty warm for it's expected use.
The rest of these arguments are just kind of pointless. Nobody is sleeping with a camper that cold so why are you expecting your battery to encounter that temp? Sure, maybe if you were loading your camper for first use and going out on a trip might the camper be that cold but be a little creative and figure out how to heat up the camper before you take off and to keep it warm as you travel. Both things that can be done without much effort.
Problem solved....