It will be far more of a financial success off the top with Bale as Batman, or at worst with JGL in the role.

Introducing a brand new Batman, the face of DC in the film world, as a co-star in a Supes vehicle seems like a bigger risk to the Justice League plans than they're worth, unless they know they have a home run Batman, in which case why not introduce him?

They will absolutely attempt to throw big bucks at Bale or JGL. I'd be surprised if they didn't.