It would be interesting if units had a “cold resistance” stat attached to them. This stat would do absolutely nothing unless the unit encountered cold. So, what is cold? Cold tiles would be a special set of tiles from the arctic biome that are not used in normal maps (and if they are used in maps at all its spelled out in advance, and has to be selected by the players, and its not eligible for pick on pvp scenarios)
But anyways, when a unit walks over a cold tile, the cold effect is applied. What does this effect look like? Well, the unit could be slowed. It could take minor damage. Whereas if it has cold resistance, then it does not take that effect.
Conversely, heat resistance could be a thing, for desert tiles. And if you run over a desert tile without heat resistance, you become parched, and move slower, and eventually die. Units like camels and skirmishers would have innate heat resistance, while units like champions, and other nonpikemen infantry would have cold resistance. Just a thought on biomes…