But let the zone police be in charge over the red button of wrath and mass destruction.
I'd say, there would be a quite easy and clever way to solve this problem, aswell as doing more good things in one slap.
The gas grenades, should be able to thrown into bunkers, filling closed rooms, in this case the bunkers with toxic slowly over time covering the whole and there-rot the victims to death with poison. It would make the unpopular gas grenades usefull, and once again a bought item. Also it would give a against resistance versus bunker campers and make it possible to counter attack.