I've been wanting to build a city builder using urban planning libraries like this
Imaging the simulation being running headless, decoupled from the GUI client
You can use it headless, apparently: https://github.com/eclipse-sumo/sumo/blob/53cdfa4b595500047e...
You read my mind. City builder games are unrealistic in a bad way that defies intuition and prevents you from modeling a real city. This has been my huge frustration with Cities Skylines, which looks great but where ambulances take three months to reach patients.
Slightly tangential, but there's this game: https://store.steampowered.com/app/1134710/NIMBY_Rails/