Aquaman, Cyborg, and Wonder Woman are in it, and I think Flash as well, but who knows in what capacity they'll be in or just towards the end when they build it up for Justice League.
Building on some of what you said Cap, I can see Superman have a cult build up around him due to the events in Metropolis during Man of Steel. People start to worship Superman, which causes other superheroes to pull away and let Superman deal with it all. Supes has a secret police (the soldiers kneeling in front of him have the S logo on their shoulder) to help him, secret bases/government buildings to move between and depart from whenever someone needs help, and his ego builds. Batman has had enough, decides to once again don the cape and cowl, and works on an armored suit in order to withstand the force of Superman's attacks. On the tower Batman is holding a gun of some sort, the Batmobile has some prodigious weaponry, and maybe he decides to use a bullet made of kryptonite if needs to.
Bats and Supes fight, Supes gets wounded by the kryptonite, and Batman shows that no one is above some justice. Seeing that Supes can be dealt with and kept in line, Aquaman, Wonder Woman, Cyborg, Flash, and whoever else comes out of hiding, meets up with Supes and Bats, and plan ways to work together to keep the world safe.
And then there's that Russian satellite/rocket that Supes is holding. Maybe we'll get some KGBeast in the future? Could also have Robin/Nightwing, Green Lantern, Joker, Metallo, Doomsday, and a whole host of other heroes/villains in the mix. So many possibilities!