I think the best way to approach this film was to just do a freaking Man of Steel sequel w/ Batman in it. I think that might have been the original idea, but they fell in love with the idea of Batman vs. Superman, that they developed the whole film around it, and made it a set up movie to Justice League.
The thing is the whole Lex Luthor character in this franchise was a lose-lose for DC. Either you put him in the sequel, and everyone complains "oh, another Lex movie with kryponite" just like Superman 1,2,4,Returns. 4/6 movies featured this plot, its boring... On the other hand, if you do a Brainaic movie or Metallo or someone new, then you'll hear "when are they going to do a Lex Luthor ! How can you have two Superman movies and not address Lex !".
So the best thing to do, in my opinion would have Man of Steel 2 w/ Lex Luthor, but have Batman as a supporting character. I like the idea of Batman in the background. If you look at the root of the character, Batman was an obsessed character that did not care about anything else in his life but his obsession for stopping crime. He did not care about his wealth, he did not care about relationships, he did not care about his life in a way - all he cared about was his obsessions. Now, if the film went the direction of Bruce really thinking Superman had to go, and have him in the background of the film, training his ass off, learning about kryponite.
The focus of the movie was Superman vs. Lex. Lex being a 'hero' for cleaning up and helping Metropolis after that destruction from the first film. Lex being completely jealous of Superman. Lex in his own mind believes he should be helmed as the hero of Metropolis and his upbringing of his father drilling it in his head that he is the savior of Metropolis, only to realize his dreams were crushed, and everyone hailed Superman as the hero he thought he was suppose to be.
Superman's main focus is not Lex, is not Batman - those guys are obsessed with him - his story is focusing on himself. In the first movie, he discovered who he was. This movie should be about focusing on what he wants. His story should be on the focus of adapting into he Clark Kent role and his relationship evolving with Lois Lane. Honestly, this movie should be a love story between the two. And not THAT LOVE STORY FROM SUPERMAN RETURNS !!!! I mean, a real one, where they have issues, complications.
While Superman is trying to figure his relationship out, and his place in the world as a savior, BOOM - Batman sneak attacks his ass. The thing is Batman is trying our different methods of beating Superman, he's not even sure if the kryponite will work, so he has like four different elements - and in the first battle, Batman loses, but he discovers the kryponite is the fourth element that is effective, which ultimately saves his life from getting killed by Superman, so he barely escapes, but discovers the kryponite is the element that can be used to take him out.
With Lex, anyone but Jesse Eisenberg. He looks like he was ripped right out from a Schumacher Batman film and threw into BvS world. I couldn't stand it. Someone that will take a much more serious position on the role.
No Doomsday. No Wonder Woman. No team up stuff at the end. You had a giant epic first film. The second movie should always and I mean ALWAYS take a step down and make it a more character driven personal film. Star Wars, big epic Death Star Battle. Empire Strikes Back, much more personal film, the climax was about the main characters escaping a small city. That wasn't some epic giant battle scene, but a more personal film that proved effective.
I would have the second and final Batman battle where Batman kicks the crap out of him, and nearly kills him, he tries to kill him, but then the night ends and the sun appears, giving Superman more power to get through the kryponite and end up beating Batman. But the moment Superman could kill Batman, but chooses not to, he shows compassion to the enemy and this inspires Batman to know that Superman is legit. The whole character arc of Batman is he finally decides to KILL, he feels he has to kill this one alien in order to save the planet. And he justifies it by he's not killing another human being, but an alien that doesn't belong here. Once he sort of accepts that, he tries to kill Superman, but Superman beats him - thus showing compassion and letting Batman go. This moment really affects Bruce quite a bit as he realized he compromised his morals of no killing and it wasn't a good thing, and he became the one thing he feared the most, a murderer. The 'thank you' scene would be Batman revealing Lex evil plan toward Superman that would nearly taken him out, so Superman has the knowledge of Lex plan of attack, and the final climax would be Superman showdown with Metallo, that Lex created from a deal with Wayne Corporation Tech Division.
Those would the action scenes I have in my head, but overall, its a story of Superman struggles with humanity and how this will affect his personal life of people trying to kill him. Earlier on, Superman reveals to Lois that he can't be with her due to the fact that the only thing that could really be his kryponite is her. That if his enemies found his secret, they would come after Lois instead of Clark. He realizes this through Batman / Lex. I wouldnt have had them together at the end. Save it for the sequels. End it on a 'damn' note.
Casting Amy Adams really a bad choice, imo. They chose her because she's likable and she's famous - but I dont think Snyder understood the character. Lois was suppose to be a fire ant. Thats why the relationship between Clark and Lois was always so damn interesting, because they were opposites. Clark was the good ole boy, the innocent one - where as Lois was the fiesty, dont take no crap attitude. It makes the dynamic of the characters interesting and their love story so good because Lois does settle with Superman. Once again, Snyder DOES NOT RESPECT THE SOURCE MATERIAL. Lois needed to be a *****. Amy Adams is just too sweet. I would have went with Olivia Wilde or Zoe Saldana. Metallo maybe Adam Driver ? Lex, the Billy Zane, Bryan Cranston would be too obvious. I like that they tried something new with Eisenberg, but it just failed. They tried and didnt succeed. I like the idea of someone like Denzel Washington, maybe. Someone not really into comic book roles. Maybe Jon Hamm would be interesting in that role. Or Arnie Hammer. And for Batman, I liked Affleck in the role, but I would have never casted him, lol....
Jake Gyllenhaal would be an interesting Bruce Wayne after seeing him in Nightcrawler and seeing how he can transform into a role.
I could write out Metallo & Lex and all that, but I wrote too much already.