The pre-Identity Crisis Rogues Gallery, back when DC supervillains weren't all-in on murder and rape, would be a great model for this, or the old Secret Society of Super-Villains. You could have all the fun supervillain economy NPCs like the Crime Tailor (
a real character!) and so on helping the PCs and providing them info on jobs, letting them essentially pick from job boards.
And true to the West Marches model, the players would have to figure out what areas of the city which superheroes operated in, at what times of day, etc., and figure out where safe places and times to operate would be.