I think this could be a fun show, but how well it would work depends on the Gordon's supporting characters. I could see A.D.A. Harvey Dent continually frustrated by the fact that too many of his organized crime cases fall apart due to police incompetence or corruption, but he notices the cases he gets from Gordon are solid, and get him convictions. He pressures the mayor to set up a special task force headed by Gordon to work focus on organized crime, and cleaning up the GCPD.
Gordon would basically form his own version of the Untouchables, the cleanest cops in a dirty department. Maybe add rookie Renee Montoya, and detective Harvey Bullock, a rough around the edges dick who, while he may short cut procedure from time to time, gets the job done.
Oswald Cobblepot would run the Iceberg Lounge, and be a leading organized crime figure.
I would make Edward Nygma a P.I., obsessed with solving crimes, as if they were puzzles or crimes. He would compete with Gordons squad in solving crimes. Sometimes they would win, other times he would. His turn to villainy would come when the Batman comes along, and he can't solve crimes before the crusader, and his focus becomes solely to beat the bat.
Selena Kyle would be a cat burglar. She wouldn't be a costumed villain, but perhaps dress in all black with a mask. A camera catches her in the act at one time, and while they cannot make out any details, they can definitely tell she is a woman, and is nicknamed the Catwoman by police.
Add in many of the mobsters from the comics and you have plenty to play with.
And perhaps... Batman won't appear, but who says Bruce Wayne won't?