I just read the Geoff Johns/Richard Donner Brainiac comic from like 15 years ago (yeah, I know, **** Johns) but it’s a really cool story that I think Gunn could merge with the DCAU Brainiac for a Superman sequel, or a Superman/Supergirl team up movie. Kara has really good arc in the story, as a lot of it involves her past trauma fleeing Krypton with her family from Brainiac’s attack. Plus the DP crew all have roles and they could fit in well with an adaptation of this story too. Lois and Kara have some nice bonding moments too. The only thing I would scrap would be the Pa Kent stuff, which seemed to just be thrown in to tug at the heartstrings.
I believe Gunn said this story was one of the ones that helped inspire him while he was working on the first movie. That may have changed since we know he initially considered using Brainiac but later dropped it. But given where this story went with Kara, maybe Gunn can drop some Brainiac teases in the Supergirl movie that lead into the next film. I feel like that could really bring together a huge story for both heroes and an introduction to the villain that everyone wants to see.
A few things I might streamline…
I feel like Brainiac works best as Kryptonian AI program rather than a Coluan scientist. However, I feel like he could have a series of organic Coluan clone bodies that he uses to give him his classic green humanoid appearance. But I stil like the idea of Brainiac as this cold, calculating entity purely driven by knowledge, superiority and experimentation. Making him a pure machine sets him apart from a more emotional villain like Lex and I want them to lean into that.
Collecting bottle cities is interesting and can make for cool visuals but I worry that it treads into some of the same territory that Luthor did with his offworld prison. It’s not entirely the same but it puts Superman on a similar path where he is freeing people from a secret prison again. But that might be okay if we get to see him explore Kandor and really connect with his Kryptonian heritage.