The game should be a mixture of Sims, and fun.
You are a top vault specialist and bidding on contracts and the war effort your convince people to pay you money to have a fallout shelter built.
The fun come in in choosing the location in the city, and what you will put in your vault, that is if you can afford it. It would be a fun game that builds up suspense for the next fallout 1st Person game, where your vault will appear, and will have patches for cool things. So you practically build the vault that will be in the waste lands, but remember the people in the past don't know there will be a fallout event , so going to extreme on robots and certain defenses, might make you go bank ruby, and the wastelander in the next game will find your corps and no one else since you could not finish your project.Plus some people don't want to much, some just want enough to start out slow, of course the question is will you be the brotherhood of steel, tech coming out, or will someone find your vault in ruin starting out.ooohh and if your people don't make it to the vault before the bombs drop , well you might be a frozen icicle starting out in the next game, or if you start to early, they may think your crazy keeping them in, and you might go to jail before bombs drop, yay dicesions.