Fallout: T=0 would be a open world game modeled after fallout 3 with an emphasis on physics. You would play as the ghoul you meet in the first fallout games (Lenny). You would see the bombs drop while doing contract work for the military at west point, which is where you would learn the controls while running to a fallout shelter. After running through the tutorial you will barely make it into the shelter and the force of the bombs will slam the door, looking around the room you will see Geiger counters with the needles all to the right of the device. It's around the time that the player realizes that radiation travels faster than an explosion that your character collapses in front of a clock.
Your character opens his eyes and by the looks of the clock 3 hours have passed. You stumble to your feet, walk towards the door, and emerge into a partially destroyed west point. The building is barely standing so you will have to tread carefully or you might collapse the floor. After you emerge from the building, the game goes open world. Basically your objective will just be to survive the new, nuked America.
So far thats all I've thought out, so if you have ideas for the storyline suggestions are appreciated.