Give HP to some doors, so large beasts can break them, also player and (even more importantly) human enemies with powerful guns, melee and explosives can blow them up. Different kinds of doors can have different HP and resistances, for example "curtain" type door is weak to bladed weapons, while thick metal door has very high mech DT/DR, but low heat/energy DR. Or fence gate with no acid resistance but high explosive DT and so on. And destructible walls too! But not like we have now - "look! this one specific tile can be destroyed with jackhammer or tnt! Rather, to make it less obvious, remove markers from "weak" walls, and allow some of them to be destroyed with something other than mining equipment.
Pros:
Less AI abuse!
More secrets that are not (ingame) PER checks!
Better, immersive gameplay!
More ambush encounters fuckery!
Cons:
???
