I believe that if Vito had had his way, Michael would have finished law school and run for Congress in Vito's old Little Italy neighborhood, where the Corleone name was still magic. Vito would have channeled his labor support to Michael, who could have shared it with Congressmen who'd support him. Then, "Senator Corleone, Governor Corleone." He'd work to legalize gambling--if not nationwide, than in New York. The Corleone gaming interests would be used to dominate legal gaming. Sonny would be in charge of a decreasingly important traditional Corleone "olive oil business."

If that's how it would have turned out, it would have made an interesting subplot: rivalry between Michael and Sonny for the entire Corleone interest--legit and non-legit--perhaps leading to violence.