What if Ice Age people did not need a snow suit? Because they are aclimated to the area? Like Eskimo's are to the far north?
But those coming from other ages not adept at the cold would need them when they come in to survive.
And the same for those from hot areas, like the Lava Flats.
Though i think the Lava Flats is supposed to be uninhabited.
But if there were people there, if those characters did not need a heat suit to live there.
Only those coming in.
Though having those from the Lava Flats required to have a heat suit when they 'left' the flats for other areas, to maintain their very high body heat requirements. Or the same for the Ice Age people wearing snow suits to maintain their cold body temperatures, in other areas than their 'Home area' might be interesting.
Just some thoughts,