In retrospect, building the League around/behind a reluctant Batman makes a lot of sense. Make Nolan's Batman trilogy the Justice League's equivalent of the Captain America and Iron Man movies. Iron Man was far more grounded than any of the other Avengers movies ... and Captain America was the original. Make Batman both the original and the grounded ... and then add the fantastical to that already-developed character.
It answers a lot of questions about the inconsistencies between the Batman Universe and the rest of the fantastical DC Universe ... like, why didn't Superman just fly in and pound Joker into oblivion? He didn't because he wasn't there.
I also like the concept of Nolan's Frank-Miller-style TDKReturns Bruce Wayne telling all these flying freakos to get off his lawn ...
... because the truth is, Wayne wouldn't want their help, even if he needed it.
I disagree. Adding Superman to
that universe would be perfect. It would require the appropriate amount of shock and awe at a flying strongman with a cape ... in a universe where that isn't run-of-the-mill. Part of the problem with an overly fantastical universe is that the fantastical is mundane ... too many aliens, and superpowers, and flying people, and whatever. The awe is gone, and Superman is mundane. In Nolan's universe ... he wouldn't be.
SnakeDoc