It might be that Batman is too valuable as a movie franchise for them to risk overexposing the character on TV.

The problem is the idea of Batman as Detective is not one that is commonly held by the masses. The biggest exposure Batman has gotten in pop culture has been the movies and the Arkham games, in both of which Batman has been reduced to a badass-I'm Batman as he kicks ass and pulls a gadget out of nowhere to deus ex machina the conflict is the prevailing image of the Bat. A detective themed show would play against expectations and likely be poorly received by all but old school comic fans. There would also be an expectation of the parade of costumed villains, and a continual stream of high profile guest stars to fill those roles would add to production costs. Also what time slot-too violent or gritty and you move it to a later timeslot and lose the younger demo except on after airing viewings (Netflix. DVR, Tivo, Hulu) etc., go for the earlier slot and you have to lose some of the edge to meet standards and practices, but advertising money (which is what fuels the broadcast schedule and pays for production) is dependent on time slots and shows can live or die on what day and time they are slotted into the schedule.

What version of Batman would sell to a mass audience? How does that fit into the puzzle that is the weekly broadcast schedule and how does that affect advertising dollars available to pay for production?

You can also be sure that no live action show will be on while Gotham is on the air and it has already been renewed for a second season. If the show gets a third and hits syndication, there will be a need to let the ground lie fallow before new versions of those characters are attempted on network tv as well, so there are a lot of hoops and obstacles that have to be dealt with before a pilot would even be commissioned for such a series.

-M

I think we need an uber serious Batman show where, once an episode, he breaks out into the Watusi.

The problem isn't DC, it's whether advertisers/studios would invest in another product concurrently which dilutes their brand and revenues stream. Shows don't  get made unless advertising dollars are there. Money form the back end (subs services, DVDs, etc. don't defray upfront costs of production for the studios/networks, advertising dollars do, and if advertisers see it as a bad risk, then they will not back it. Why invest in a Batman show on one network, when there is already one on another that has its audience already and it's ratings share-that show weakens the likelihood of the revenue stream from the new show being worthwhile. Now if Gotham goes off the air, and there is a void, exploit it, but you won't see two American networks having the same show with the same established characters in competition with one another. DC has no problem diversifying their revenue stream with multiple versions of the same properties, however the money men who make that possible just might and the decision is theirs, not DCs. 

-M

Just as a guess, I imagine that the rights to adapt Batman himself may be priced higher than most TV shows are willing to pay. I assume that GOTHAM pays a lower rate just to adapt Bruce Wayne and various Bat-characters who are not-- and may never be-- given their superheroic cognomens. And does anyone remember how BIRDS OF PREY solved the problem? They alluded to Batman and Catwoman in the first episode, and sent Batman out of town for the remainder of the series.

Though it might be a case of "robbing Peter to pay Paul," I think it's very likely that one division of Warner's probably does have to pay another division. I can't cite a specific case, though, so we can agree to disagree.