I have an overactive imagination. I have a few plots in my head going and im ignoring them and focusing on this one.
If you need inspiration, look into the legacy and challenges thread. Even if you dont want to do them because some find the rules restrictive and the game becomes chore-like, the challenges serve as great brainstorming points. Like.. the 100 baby challenge - what kind of sim wants to have 100 babies? Or the rags to riches challenge - why are they starting out with just rags?
Theres historical challenge, rotational gameplay, building challenges,mafia challenge. Im sure one of it will get your gears going :)