Would be kinda interesting to make something like Orteil's murder games thing but running a proper full simulation of character and world state.
No idea how it'd actually work implementation-wise but I'm very tempted. Simulation stuff like that always catches my attention in just the right way. Whenever I play the Sims I don't ever actually want to play the game. I wanna make a bunch of characters and model their personality as accurately as possible and watch how they autonomously interact when put in the same space. (Which is one of the reasons I hate TS4, feels like the autonomy is so mind numbingly dumb. Everyone just sits around reading books if there's a bookcase or whatever. Sucks.)
This fascination is basically the whole reason I love game AI. I like working on stuff like MP bots because I wanna give them realistic behaviour, personalities, the ability to form basic connections and relationships with other players, then dump a bunch of them in a map and watch what happens.