I actually saw a comment on a forum by some guy with a pretty accurate idea of the MoS 2 sequel idea. I’m giving him partial credit on here (even though I have no real name),his basic idea is Batman collects a proto justice league against Superman with Lex initially as his ally. When I thought about it seems incredibly plausible and so I have elaborated and expanded an idea on how it could happen.

I think the movie starts out say 2 years after the events in MoS with a large portion of America divided between those thankful for Superman saving them from Zod and another bitter and fearful of the damage caused and power wielded by Superman. I think the movie may approach Lex as the champion of humanity seeking a containment policy on Superman, he and Batman have both been helping to rebuild Metropolis with their vast resources and start out as allies with a common cause of containing Superman. Lex’s idea is Kryptonite …unearthed by Luthorcorp (source- residual mineral discovered in areas affected by the earth engine during the terra forming process).He offers it to Bruce Wayne to bring down Superman together. (obviously he does not know Bruce is Batman) Bruce takes it upon himself to do this in his alter ego form as a last hurrah I guess, coz he's planning to retire from his crimefighter by moonlight life anyway. He finds out Superman is Clark and laces his weapons and suit with Kryptonite in various forms and goes to confront Superman in Smallville .After defeating him, he lies to Lex that a meta human he knows owed him a favour and he has Clark in his vault at Wayne industries but Lex demands Superman as his prize since he gave Bruce the Kryptonite. After taking Superman to Luthorcorp. Batman using Cyborg who is his Pentagon liaison and DoD-DARPA contact finds out Superman has become a lab-rat and so Batman asks WW (whom he has known as a Themiscyra emissary) and Cyborg (who joins because the Government has a stake) to rescue Superman. We find out Lex made a deal with the government and promised to make them a super powered army. He is confident because he has a meta-human of his own, his prototype/subject 0 is Parasite (played my Jason Momoa) whom he plans to use as a template to create a Kryptonian army for the government, but what the government does not know is Lex has also developed an army of Metallos fuelled by kryptonite to have the ultimate power for himself. When Batman comes to Lex’s facility demanding for Superman and telling him he knows what Lex is up to, Lex realises it's Bruce and calls him a traitor to their common cause and orders Parasite to kill Batman and WW. Batman is clever enough to deduce that Parasite has taken Kal El’s strengths and weaknesses as well so while Parasite is besting WW defeats him with Kryptonite. Batman apologizes to Clark and sets him free… We then have Lex release his Metallo prototypes to defeat the heroes and so in the climactic battle Cyborg, Wonder Woman and Batman battle the robot army of Metallos, while perhaps Lex has developed a unique power suit for himself perhaps laced with Kryptonian nanotechnology like the defense system of the world engine and he battles Superman in the finale, with Clark having a choice to destroy Lex with the suit but this time he somehow destroys the suit and lets Lex live so in the end Lex is in jail and we have Clark gain new justice league allies in Batman , WW and Cyborg.

Is this feasible?... Your opinions please