I'm having some similar concerns over my own first battery box.
When you heavily charge and discharge, your batteries (and conductors) will generate heat, and especially in hot conditions (I'm in Texas) this is a bad thing -- you'd want to ventilate.
When you are camping in a cold condition, near and under freezing, your LiFePO4 batteries will be damaged when charged at that temp; in this situation you want NO ventilation, and instead some heating (heating mat or other), and you'd not want to leak the heat to the outside world and be very inefficient.
These aspects make the battery box design more complicated and interesting. It makes perfect sense when most folks recommend to put the batteries INSIDE. This is where you expend energy to keep conditions moderate anyway, as least while you are using it. Unfortunately there's no such thing as electrically-controlled insulator which can magically go from conductive to insulative -- at least no that i know of.
I had designed a crazy box where the batteries were all surrounded by mineral oil, which could be heated or cooled with a liquid-to-liquid heat exchanger which could run either heated or cooled water into the control side. It would have been super overkill, and if it were the only bit of project I had in front of me it would have been super fun.
Best reasonable way to do it would be some sort of thermostatically-controller forced air cooling, combined with reasonable insulation and a thermostatically-controlled heating pad. When the fan is off, the insulation works ok; when nearing freezing the pad will heat up the batteries to say 38 to 40 degrees F, and when over a certain internal condition the fan would come on and heat the batteries.
As it is, I think I'll just put heating pads under, wood around, and forced air into the box at the edge to run around and over the batteries as described above. I'll put the temp sensor in the middle of the pack. Best I can do, IMHO.
David
P.S. no, i don't care about compression of the batteries, so I could run oil around them if i wanted, or even just pack aluminum sheets between each cell.