Another idea that has kind of nagged at me from time to time is a story about sidekicks. Basically Main Hero realizes he can't fight the war on crime by himself and takes on a few sidekicks to train. They'd be high school or college age people. They'd have been undergoing his mentoring for a year or two when something happens to Main Hero. He vanishes/appears to die. So sidekicks are left to take up the fight against crime in the city and figure out exactly what happened to Main Hero. They'd be seeking to earn the trust of the few honest cops that trusted Main Hero and strike fear into the hearts of the major criminals.