Clothes in Cataclysm currently operate on the idea of providing warmth to the wearer. While it's possible to achieve in reality – which is represented by the powered thermal clothing in-game – clothing operates rather on the principle of heat retention.
Implementing heat retention mechanics would enhance survival management, especially for characters relying on saving body heat due to extreme circumstances (e.g. lizard-type mutants, or finding themselves in an Arctic-like environment). Such quality even has a unit of measure to compare against: clo.
See also: clo as a unit of heat retention
Heat retention also enables a separate, adjacent mechanic to be fleshed out: climate control.
Climate control – automatic adjustment of internal temperate in order to maintain a comfortable level of heat and/or moisture – currently exists as an armor trait. There either is climate control (most likely in powered armor and other full-body suits), or there is not.
Implementing climate control as a scalable value, acting as a degree to which the item's heat retention could be lowered or increased depending on the outside temperature, would enable a wider variety of possible clothing items, including high-performance gear (enabling extreme climates to be implemented) and advanced technological solutions to maintaining comfortable body temperature, including for heavily-mutated characters whose needs no longer reflect typical homo sapiens needs.
A more grounded notion of climate control, relevant to many non-science-fiction items, could be maintained with heat hatches. Small auxiliary zippers in some tactical and sports gear that could be opened or closed quickly to enable some temperature flow without exposing the wearer to the elements. While not a high-tech solution, it should nevertheless be considered when implementing degrees of climate control.