Gangbusters take on dungeon23. Looks like this will be a modified take on the megadungeon.
Gangbusters, a USA-focused prohibition-era ttrpg, has a setting that’s a Chicago expy. So it looks like I’ll be analogizing megadungeon to city & rooms to buildings. Steets & alleys will make good stand-ins for corridors and tunnels.
Gangbusters has classes & xp, so factions & building occupants should be easy to implement.
Each day will either be a broad overview of one of the buildings or a dive into the rooms in the building. For inspiration when things are almost certain to bog do, I'll be referring back to the Gangbusters rules I have (incomplete! where did the adventure and actual city map go? woe!), and this dungeon23 carrd: https://dungeon23.carrd.co.
Also: in the back of my head, as some point, this will almost certainly start to pull in variants on traditional fantasy game elements, and maybe sf & superhero. Why not? I recently saw a pic of some gangster orcs in an autobody shop, and it appealed to me.