It starts out right before the bombs drop, you are rejected from joining others in the Vaults, so you decide to move to a very hilly, rural area, to protect yourself from the coming apocalypse. When the Great War happens, you find yourself in the middle of a lawless region, with a fairly well stocked cabin. Instead of a main plot or quest line, there should be a dynamic system that would make each new game unique. The survivers in the surounding area would react to there situation in diffrent ways; for example, a local towns sheriff could be a noble, intelligent person who rallys the town into a trading post or fort, or a cold, sadistic person who forms one of the first raider groups, or a pathetic Barny Fife type who gets killed and the town has to find a new leader. Other groups would form, some who try to retain there civilized ways, others who raid and pillage, and others who just try to survive the best that they can.
You yourself would have to decide how to survive; stay in your cabin, wich would be a good place once it's fortified, but a very obvious place for others to attack, leave and join one of the towns, form a raider gang of your own, become a reclusive paranoid hermit, or many other options. Tell me what you think of my idea, and how it could be better.