I find it a lot silly that there aren’t different weight stat sets that have both a heat and cold protection armor set. For instance, there isn’t a light accuracy cold protection set. Hell, there are few light sets at all with cold protection, and the stat distribution across the cold sets leave much to be desired.
I think the least intrusive solution is armor kits. Crafted like other kits, but in this case, heat or cold protection. Kit over-rides default temperature protection. Two types of kit of temperature protection: basic (one pip of protection) hot or cold; and advanced (two pips of protection) hot or cold. Four kits altogether.