I have a feeling you've never done it before
Trust me it's easy.
Our ripoff we'll be called Afterglow, For our rip off we'll pick New Mexico. The bomb shelters will be called Sanctums. Pip-Boy can be Pid-Man. Our main factions will be called Order of Steel, Directorate, Co-Prosperity Union, and Disciples of the Mushroom cloud. Our "Raider" factions will be called The Red Tide, Copperheads, the Brakemen, and some generic bandits. Minor Factions will be Children of the Church and Rail Gypsies. Some of our Communities will be Rail Junction(Santa Fe), Glow Sands, and The Crucible.
Our monsters and will be Giant Scorpion, Camel Bug, Gila Monster, Mega Copperhead, Coyotes, rabid dog, Death Stalker(death claw), Sand Rat, Sand Hawk(Cazadore), Long Horn, Ram.
The player's home has failed power generator that can only be fixed with a replacement part. They are running on back up power, but they need the main generator to sustain life support systems. They want nothing to do with the outside and they need you to find the piece. Said piece is locked up in an abandoned bunker that the main factions want a hold of for some reason. Had this been a game instead of Fallout, people who had never heard of fallout would have called this a unique game.