In an interview with Forbes, Snyder admitted that the idea to revisit Bruce Wayne had been with him early on in the sequel-planning process, but explained that the character's presence in the film wasn't a shoehorned excuse for a reboot so much as a natural foe for the Man of Steel.
Snyder added that he was still planning on taking much of his inspiration for the character -- set to be played by Ben Affleck -- from Frank Miller's comics, with the goal of evoking an emotional, thought-provoking response from moviegoers.
I gotta be honest, it definitely was a thing that... after Man of Steel finished and we started talking about what would be in the next movie, I started subtly mentioning that it would be cool if he faced Batman. In the first meeting, it was like, "Maybe Batman?" Maybe at the end of the second movie, some Kryptonite gets delivered to Bruce Wayne's house or something. Like in a cryptic way, that's the first time we see him. But then, once you say it out loud, right? You're in a story meeting talking about, like, who should [Superman] fight if he fought this giant alien threat Zod who was basically his equal physically, from his planet, fighting on our turf... You know, who to fight next? The problem is, once you say it out loud, then it's kind of hard to go back, right? Once you say, "What about Batman?" then you realize, "Okay, that's a cool idea. What else?" I mean, what do you say after that? ...But I'm not gonna say at all that when I took the job to do Man of Steel that I did it in a subversive way to get to Batman. I really believe that only after contemplating who could face [Superman] did Batman come into the picture.
" ... Batman and Superman ... teach us about ourselves," the director said. "I think Batman - now after Chris [Nolan]'s movies and the way we track Batman through his cinematic history - he does have this license to enter our world and be a real character and not a complete cartoon, and he's able to tell us about the way we live and our society. He moves with us, his morality - I think Superman probably less so, but I think Batman definitely sort of reflects us in a more personal way."
"Batman vs. Superman" hits theaters May 6, 2016.