Batman vs Superman director Zack Snyder reportedly intended for Christian Bale to participate in the film, but with a totally different role. Instead of the wonderful Bruce Wayne, it was about him being Lex Luthor.
According to this news, we could have seen Christian Bale in 'Batman v Superman: Dawn of Justice', but from a different role.
One of the reasons for this alleged change is that Christian Bale was not satisfied at all of his portrayal of Batman in the trilogy directed by Christopher Nolan. Bale has had no qualms about admitting that the role of Joker, played by Heath Ledger, intimidated him in many moments of the shoot, as he was a character of a more marked and developed character, and from that moment on, he did not know how to give Batman what he would have wanted.
This dissatisfaction of Bale is what has motivated that I did not want to resume the trilogy, and that the new Warner superhero movie gives this responsibility to Ben Affleck. The integration of Superman and Batman would not have been possible in the realistic universe created by Chris Nolan, because Superman is a superhero with many more fantastic nuances.
However, in Batman vs Superman, Zack Snyder was always clear that he liked to change the actor for the role of the bat man, because his vision was totally different from Nolan's, but he did consider that Bale was in another role in the film.
Although in the end an agreement was not reached, it may be that in future films, Christian Bale can compensate for that bad taste in his mouth that the Batman trilogy left him, playing different roles in films of the saga. What character could Bale have played in the new film? It is said that it would have been a real Lex Luthor.