how about this: the story takes place just in the time of the bomb, you are ripped from your family and put into a vault. For the first part of the game you are doing errands so that you can get out of the vault because the people will not let you out because they fear the radiation will come in but you want to go out to see if your family survived. When you finally get out you begin looking for your family by searching for nearby vaults to check if they went for cover there. After about the 3rd town you visited, you find your old house and its completely wrecked, but through the rubble you happen to find an envelope from your wife, telling that they headed to a Vault 13. Before you arrive there you get a desert encounter watching two brotherhood guards fighting 3 super mutants. The brotherhood guys take 2 of them and one of the mutants shoots and melts the brotherhood guy and one mutant versus one brotherhood, the screen fades and it says : 3 hours later it shows them punching each other and showing the subtitle :panting: or something over both their heads then finally they just start laughing and walk away(this is supposed to be jacob and marcus from fallout 2). When you finally get to vault 13 you see the enterence and start running towards it but see that the control panel outside was eaten apart by rats. you turn around and walk away/ a new quest is added: find parts and tools. for this you go to a nomad town called Shady Sands it's populated by traders and thugs when you get there you are prompted by a thug with talking head for cash if you say no he attacks you but when you get him to almost dead he stops and says "WAIT WAIT ill do anything I'll do freakin' anything just don't kill me" you get 2 options, kill him and take his stuff and watch his thugs run away or option 2: tell him to come with you and guide you around the wastes or else. as you travel with him you can talk to him and you find out his name.bla bla bla and in your travels you come across a dirt field that he leads you to you ask him what its about bla bla and he opens up a manhole covered with dirt. this is the entrance to vault 14 a long abandoned vault infested with giant ants and rats(of all kinds) and when you reach the bottom level you find a computer module with the parts you need. Finally you've got them and you work your way out. you travel all the way back to the vault 13 cave and no matter where you look, you can't find the vault you travel for days when finally you collapse and the thug leaves you for dead.
Good story huh? I made it up right on the spot!
well anyways comments---
I think its hardcode in engine and unable to change this.