Re: Should they introduce Kara Zor-El in the sequels?
I've never been a fan of surviving kryptonians besides Kal-El, he should really be "The Last Son of Krypton".
When I've thought about how to introduce Zod and company, I had this idea of "The Phantom Zone" being a place where the conscience of kryptonian criminals were preserved, maybe as complex artificial intelligences that simulated their thoughts/consciences/brain waves, and the only way to be free again would be "downloading" said consciences into clones created from conserved dna. How could Zod and other kryptonian criminals be released on Earth then? Brainiac would have access to both The Phantom Zone and the dna samples of Zod, Faora and the rest.
They wouldn't be "real" kryptonians, but copies/clones with the same minds (also copies of the originals). The "real" kryptonian villains would be executed after extracting a dna sample and a "mind/brain" copy of them that is preserved in The Phantom Zone, so if the Krypton Council decided to "free" them again, they would create a clone where the memories/thoughts/conscience of the criminals would be "downloaded" from TPZ, and this way they would be "reborn" according to kryptonian beliefs or something like that.
But once Brainiac brings Zod and the rest back, the clones don't last as much as expected because Brainiac gave them a limited life time so they wouldn't turn against him or become a future problem, so they eventually die with Superman being unable to save them. If any writer wanted them back, more cloning and more conscience downloading from TPZ and done.
MoS will probably not do any of this, and I don't know how Zod and the rest will survive and come to Earth, but I just love the idea of Kal-El being the last surviuvor of his home planet and Superman/Clark and Lois' future children being the only hope for kryptonians to survive.
In future stories I would like to see Lex using Brainiac's clening technology to eventually create Bizarro while trying to create his own Superman clone, an evil and not so dumbed down verion of Superman who thinks that he is the real Superman/Clark until his body and mind start to spoil, and then his hate for the real Superman turns him evil.
And once Superman is presumed dead after fightning Doomsday, Lex could become president of the USA and create another replacement for Superman called Superboy, a younger clone because Lex couldn't duplicate Brainiac's cloning technology with Bizarro, and the only way to keep the clone healthy and sane was to make him permanently young before his body and mind were spoiled like Bizarro's. This "Superboy" could eventually travel to the future to join the Legion of Superheroes because he felt out of place in the present when the real Superman came back, but he could return once in a while through time travel to fight along the Teen Titans/Young Justice and to say "hi" to Clark, living both in the present and the future.
And Kara? Not a clone, and not a real cousin either, but a descendant from the far future that comes to the present sent by his father to warn Kal-El from some deadly danger like Doomsday or Darkseid. She would be actual family for Supes, from maybe one of several space kryptonian colonies of Kal-El's descendants that left Earth centuries ago for some reason, and maybe said colonies are in danger because of an ancient menace, one of Superman's villains, so Kara's father sends her to the past to warn Superman about stopping this villain because these new kryptonians of the future maybe many of them are not as powerful as the originals and/or because they are pacifist sciencists that are not used to fight against a powerful enemy.
Then Superman and Kara would realize that the only way to save the colonies is with Superman and/or the JL travelling to the future to stop this menace, and once Superman goes back to the present, Kara tells her dad that she wants to go with Supes because she has been living in the past for a while already and she just loves it, so Kal-El and Clark tells everybody in the present that she is his cousin to simplify everything.
Think about Trunks in Dragon Ball Z and how he travelled back in time to warn Goku about the androids that have ruined his future, this could be similar.
I've thought about these ways to introduce these popular characters without changing their stories too much and keeping Superman as "The Last Son Of Krypton" for real. No Superdog, Superhorse, Supermouse, etc... Maybe a dog called Krypto by Clark in the Kent's farm with no superpowers and no real kryptonian connection, because nobody would buy a Superdog these days except maybe children in an animated show just for them.