It would indeed require a lot of programming but I don't think it would be an unrealistic amount. It would involve implementing (on a more visually appealing scale) the same programming from scribblenauts along with a set number of random scenarios. So you want a frying pan while walking down the street. Someone drops one out of a window. You want a pedestrian to be killed. Random hit and run or shooter appears. Give things monetary values like Fable (actually I imagine it like a cross between GTA and Fable) where you can buy houses. But unlike most games you start out with a set amount of money. So in this since it is like a sims game but instead of a set number of days you have the money.