1. Jim Gordon stars in Your Basic Police Procedural
It should be noted that the series is being helmed by Bruno Heller, who has previously created "Rome" and "The Mentalist." The first has its fans and the second is popular if generic, yet neither is the kind of must-see, ground-breaking TV that you'd hope a creator has on his resume. This isn't to say "Gotham" couldn't be awesome, as it's not like a showrunner isn't capable of a breakout series or that every proven showrunner makes nothing but classics every time out, yet just imagine the level of excitement if, say, Vince Gilligan was behind this show.
It could very well be that "Gotham" becomes a more comic geek-friendly version of Mentalist, with the GCPD solving a new case every week and maybe one larger arc (a la the hunt for Mentalist's "Red John" serial killer) taking place over the entire series. That larger arc could be the battle against the mob, certain major-but-more-mob-based Gotham costumed villains coming to prominence (Black Mask or Penguin, rather than Joker or Poison Ivy) or maybe the arc is just Gordon's rise to commissioner itself. This would seem like the biggest waste of all, taking the rich premise of a pre-Batman Gotham and just making it into Gordon solving a case-of-the-week.
2. Jim Gordon stars in Bigville
The other bad option, in my view, would be to have "Gotham" be "Smallville." Now, in fairness, I wasn't a Smallville fan though the show was certainly popular enough to run for 10 seasons. I just didn't care for how a show that was allegedly about Clark "before" he became Superman basically just shoehorned every Superman character and gimmick they could into the series in an attempt to create as much fan-service as possible.
This shouldn't be "Gotham," either. The concept seems to be a show that's pre-Batman, not "everything about the Batverse except actually have Batman in it." The latter would just seem empty, and if Batman does end up being a character without actually showing him, then that's doubly pointless. Batman becomes either Poochie or a deus ex machine in that scenario.
3. Jim Gordon stars in James Gordon: Year One
One major question I have about this series is just how far back they're going in Gordon's life. If it's Gordon as a young cop joining the Gotham force, then just by timeline alone, there can't be any traces of Batman.
I feel like this idea would share similarities with the "generic procedural" concept, though it's also almost too limiting. I don't want the series to be overwhelmed by Batman-related stuff, but obviously the series needs SOME reference to the source material, otherwise what'd be the point? Setting the series too far before Batman's emergence would negate too much of the mythology, and also cut out some of the intrigue in Gordon's actual personal life.*
One interesting idea I've seen elsewhere online is that while Batman and Bruce Wayne can't be characters, that doesn't mean Thomas and Martha Wayne couldn't. What if it's set early enough that Gordon actually befriends the Wayne parents early in his career, and their murder is the first season finale? Gordon's attempts to solve the Wayne murders could be the aforementioned "big arc" of the entire series.
* = by this, I mean Barbara Gordon, who absolutely needs to be a very smart, intrigued-by-police work teenager in this series and played by a hell of a young actress. Just the idea of Barbara-as-Veronica Mars is good enough for a series in itself.
4. Jim Gordon stars in Gotham Central
"Gotham Central" was an acclaimed comic series by Ed Brubaker and Greg Rucka earlier this decade and in a perfect world, this would be the idea being translated to TV. Basically it just focuses on the GCPD's daily business of operating in the crazy world of Gotham --- it was "Hill Street Blues" if that show had taken place in a city with a Batman. While I said I wanted at least some clever reference to the Batman source material in this new show, I could live with just minimal reference if it meant a really good, gritty cop drama was on my screen.
Interestingly, Commissioner Gordon was only a minor character in the "Gotham Central" series but obviously if he's just a beat cop or detective himself in this show, he could be inserted right into the everyday police mix. The timeline could also be played with so that Gotham police supporting characters like Renee Montoya, Harvey Bullock, Crispus Allen, etc. are all Gordon's peers rather than his future proteges when he's commissioner down the road. This could also easily be merged into the "Year One" model for a great cop show that's not a case-of-the-week premise but rather basically the Wire's type of police storylines.
5. Jim Gordon stars in (Just Before) Batman Begins
This would be my preference since it basically serves as the best of all worlds. It's difficult to balance both a gritty, realistic cop show amidst the superhero elements but if it was pulled off, you'd have a masterpiece of a program. In my view, the perfect series finale for this premise would be Gordon finally meeting Batman, who for the previous one or two seasons had been operating in the shadows as an urban myth. Gordon may have met Bruce Wayne in a one-episode cameo before this, but Batman himself shouldn't emerge until the very end of the show's run. Legally, I'm not even sure if the character of Bruce Wayne/Batman would be available to the FOX Network but if Gordon is going to be allowed, I see no reason why other Batverse regulars can't pop up.
If you set "Gotham" just a few years before Batman appears, then that gives you free reign for almost anything. In this hypothetical show, James Gordon arrives from Chicago and dives head-first into tackling Gotham's corruption. He rises through the ranks relatively quickly and is commissioner for the last season or two, so you can have Montoya, Bullock and company as his peers to begin with and then mine stories out of Gordon suddenly becoming their boss. You have teenage Barbara adjusting to life in a new, very dangerous, city. Gordon can have regular meetings with new district attorney Harvey Dent (who's a good guy in this series), police psychologist Jonathan Crane (who Gordon doesn't trust), teenage delinquent Roman Sionis (whose crimes are covered up by his powerful family) or hell, even calls in Dr. Victor Fries to testify as a science expert in some random case.
* = another idea I've been elsewhere online would be to avoid having Bruce or Batman on the show…but Matches Malone is a recurring character in Gordon's investigations into the mob. For non-comic fans, Matches is another of Bruce's alter egos, a fake identity that he uses to go undercover within the Gotham underworld. Having Malone pop up would be the kind of very clever easter egg to fans that works a lot better than the overt, Smallville-ian method of simply having the comic characters just flat-out appear.
The sky is the limit for a Jim Gordon TV series if it's done properly, which of course is the big (non-Riddler) question mark here. I hope Heller has it in him to deliver a show that is both entertaining, creative and does justice to a great character with over 70 years of legacy.