Some areas could have a locked door ou lockbox, with a lockpick tool you would be able to open it. It would require some seconds to open and it would expend a tool charge. Locked doors would be an great acess point for areas and locked box could contain money or special itens (new throwing knives and bolts would be nice).
In my opinion players should be able to destroy the lock with grenade/dynamite/heavy melee weapon. Adding lockpicking trait would also be great addition, where you wouldn't need to carry the heavy melee weapon or waste your explosives. I'm only referring to the lockbox, since destroyable doors already exist.