Something with ties to street gangs? And the union racketeering angle has never been fully explored. St. Louis in the 70's with relations to the Syrians, that would be a good fit.

Maybe Montreal during the Rizzuto era. It was said that Vito was the only one who could put an end to the bloody biker wars, it would include every gang in the city, plus a different country with a different culture.

Was there every a French Connection movie with the mafia angle? Includes Buffalo, Cotronis, and Carmine 'Gribbs' Tramunti, as well as the Corsicans and Luciano in Sicily. That's enough for an original series.