Additional environmental protection as a tradeoff

[Elver]

Given that we now have increased lethality in hostile environments, it would be nice if we had the option on various troops to add some optional failsafe/redundant/supplementary environmental protections in hostile environments. Basically, a way to add some mitigation to the environmental kill check at the cost of additional resources to produce the unit (and/or possibly a modest combat penalty, or for vehicles, more weight/less speed), so you can have more tradeoffs. The idea would be to move towards making it so there's not always a clear single best unit loadout, even in tactical terms.

It might also be good to give fortified infantry some minor mitigation against environmental hazards as well. Going out and attacking places far away from the relative safety of your dome should be scary.