Man of Steel 2: Lex Luthor is Donald Trump.
Wait, wait, hear me out.
Luthor, unlike his real life proxy, can actually be quite brilliant and cunning. He uses the mess made by Superman and Zod's fight as an excuse to invest a BILLION in aid along with pushing government legislation through his lobbying groups to rebuild Metropolis. The people love him.
He also uses his philanthropy as an excuse to meet and try to seduce Superman. When that doesn't work, he becomes a representative of the "angry, rich old white man" population in this country. If Superman is the ultimate immigrant fantasy, then he needs to meet the ultimate nativist. One who pours money into a PR campaign to turn the public against Superman as being "Other" and a threat to Metropolis. It would not be entirely invalid considering Superman wrecked half the city himself.
He then uses this as a cover for his real Machiavellian scheme to create a being as powerful as Superman who would obey him. Whether that character should be Bizzaro or Metallo I am unsure. Personally, I preferred Metallo growing up. But narratively Bizzaro would work.
Save Darkseid for a Justice League film. And Doomsday in many ways would just mirror Bane in TDKR (at least with the breaking/"killing" of the hero) and we are too early along for that right now.