I just read this over at Topless Robot :
This is one instance where it'd be smarter to develop these rebooted characters in different films before bringing them together so their contrasts would be sharper. Maybe in this movie continuity they'll split the difference by revealing Lex Luthor is actually Batman?
I am not expecting anything great from any kind of Justice League/DC crossover movies. I don't believe any of those characters exist in a form that will allow them to inhabit eachothers' very closed-off worlds in a live action setting. It (somewhat) works in cartoons, but that isn't the same thing as bringing it to life in the real world, with real actors.
Anyway, that line sort of blew my mind. Imagine watching the next Superman movie, where he is fighting Batman the whole time, but we never see Bruce Wayne or Lex Luthor- we see the movie primarily from Superman's point of view, similar to how we almost never see where the Joker goes in Dark Knight unless Batman is on him.
Batman will be played by a new actor, so you have no reason to think it isn't Batman, but at the end of the movie he pulls his Batmobile into a secret Lexcorp facility, takes off his cowl, and his assistant greets him as "Mr. Luthor," but with no mention of Luthor at all until that point. There is no way this movie could be as good as it just got in my head right now. Also, this totally strengthens the suggestion for Michael C. Hall to play Batman, because he'd actually be Luthor imitating Batman, and that would be the greatest thing since Dexter, which is the greatest thing now.
Think about it- how easy would it be for Lex Luthor to become Batman? Batman's superpower is money and brains. All Luthor needs is a few pictures and descriptions to make something similar enough to pass as Batman, and it isn't like Batman's armor and gadgets don't change all the time, so he doesn't need to be perfect- who's going to check his Batmobile-registration?
As far as Batman's years of ninja training- who cares? Luthor-Batman would be stalking and outmaneuvering Superman, not fighting thugs in the dark. Once he has to get up close and personal, he'd use a combination of Kryptonite and power armor, just like the real Batman would have to, and fighting style would be irrelevant. Even lame-ass Kevin Spacey Luthor could stab Superman with a shard of kryptonite, there's no skill required.
I hate Lex Luthor, because a smart guy isn't a threat when you are a god who can throw him into the sun, so anything Luthor gets over on Supes is his own damn fault. Real Estate schemes aside, this would actually be a badass use of Luthor's vaunted intellect in a way that would make a hell of a movie.