How about a mission set on a divided island (Cyprus ?) during a nuclear war ? It's 1984 and the Big One has hit. No one knows who started it because somebody went and set off a 5 megatonne bomb 120,000 m over the Alps and fried every radio set and power source from Iceland to Israel.
You are a simple civvie on the island. Like everyone else, you don't know whether or not war really has broken out or if it has then whether or not it's still going. In addition to taking out all communications the bomb also took out most of the islands transport - all of the islands fishing smacks are useless and all of the big ships have left for the mainland.
The only people who still have functioning radios are the military and they aren't talking to anyone. The few reserves on the island didn't have any hardened gear so they're no use either.
The civilian authorities are calling for calm but the hotheads on both sides are starting to gear up for a fight. No one wants to be the first to break the peace but no one wants to be the last to raid the armouries either.
Just to add to the confusion there might be some UN forces on the island too. Again, they're in the same boat - radios useless and unable to raise anyone on the mainland. Should they continue to enforce the peace ? Is there a peace left to enforce ? Just who should the Danish and Sierra Leonian troops support if push came to shove - everyone, no one, themsleves ?
You could start the mission (campaign) with melee weapons and an assortment of sidearms (GIM tossers and pistols), then work your way up to shotguns, hunting rifles and eventully the military stuff.
And of course the island isn't completely bereft of talent - local HAM and CB radio operators quckly manage to get some old valve radios up and running and start working on getting some vehicles back on the road. Who will be the first to get a tank moving again ? Should you even bother or try to get a couple of 5 tonne lorries running first ?
Of course this is all happening when no one knows whether or not they should be planning for war or the next nuclear strike. It could all just be a mistake - solar flares, an interspace n-test that produced a much larger effect than anticipated (Castle Bravo ?), aliens (!) . . .
There could be heaps of opportunities for play - anything from petty crime through to gang wars, vigilante actions, guerilla war and finally full blown military conflict (Which side manages to get to the island from the mainland first ?).
Lots of possibilities !