Daniel Atler, a producer at WB recently tweeted that Wonder Woman and Doomsday would be making an appearance in the DC Cinematic Universe in the untitled Man of Steel sequel. After much thought, here is how I believe Doomsday could come to creation and shape the story in the much anticipated sequel. Remember this is speculation and nothing of what I mention is guaranteed to be in this movie.
How Lex Luthor could be responsible for Doomsday:
From what we know about Lex Luthor in the sequel is that he hates aliens and will often refer to Superman as an alien. After the events of Man of Steel, we could see Lex Corp and Wayne Enterprises footing the bill to help repair the damage Superman and General Zod have done to the city Lex has grown up in. Unhappy with how the government is handling the situation, Lex Luthor will make a political run by entering into the presidential race where he pledges to eliminate the alien at all costs. Gaining the support of billions because of Superman's recklessness, posing the question to the country, "What if a man of Superman's power turns on the public? What defense do we have?".
There are 2 important things to keep in mind when dealing with the clean up of Metropolis: General Zod's Armour and his body. Most likely, these will find there way into the hands of the government. If Lex Luthor becomes president of the United States he will get to decide what they do with the remains. The look of General Zod probably makes Luthor sick, in which he opts to destroy the body, but puts his leading scientists under contract at Lex Corp to engineer Zod's armor into the ultimate Superman fighting machine. He's so drunk on power at this point, he wants to eliminate Superman himself. He's willing to go into his own machine and risk his life for his country because that's what he believes is right.
Lex demands the destruction of General Zod's body. Given that General Zod is a Kryptonian alien, this isn't an easy task. They need to invent new technology to destroy the body. Trying over and over again to dispose of it. Heat, Radiation, chemicals, etc. nothing seems to work. In fact, it's getting harder. But they continue trying, over and over again, exhausting all resources. Until one attempt something extremely wrong happens... General Zod wakes up as Doomsday.
I believe the creation of Doomsday will be more of a subplot, setting up Doomsday as the main villain for a future movie, maybe the first Justice League. This would also set up an interesting Lex Luthor character for future movies who, in the eyes of the public, will be the creator of Doomsday.
This is my speculation given the current rumors and news regarding this movie. I have a few more ideas as to how Doomsday may come to be and how other characters like Mercy Graves may come into the picture but I could write another article on that. Let me know what you guys think in the comments below!