Re: The last days of krypton
When I was writing a Superman Trilogy for my creating writing class, that book formed the flashback saga of the 2nd film.
The first film would have combined Birthright and Secret Origin with the fake invasion being staged by Luthor and the Govt. harnessing the technology from the crystal in Birthright to design a real Kryptonian army's weapons and ships with humans manning them, staging the invasion with John Corben leading the lot posing as an army general.
Supes would foil them naturally with the film ending with him saving the day and revealing the ruse to the world. Luthor desperately tries to harness more tech from the crystal, and inadvertently setting off an energy signal with Brainiac homing in it in the after credits, which goes into the sequel.
Second film goes Godfather Part II on everyone with Brainiac being the present day and Kryptonian villain. Johns' story forms the present day arc and this book forms the flashbacks with Zod and Jor-El's conflict anchoring the arc. Film ends with Brainiac unleashing his powers on Earth, Supes defeating him at the cost of millions of people disappearing at the end of the film.
Third film would deal with the Vanishing (taken from Azarello's For Tomorrow) and combining the story with sections of Godfall and World of New Krypton. Supes tries to find out what's happened to everybody and in turn discover's them trapped in the Bottle City of Kandor and gets imprisoned and mind-washed by Zod and his minions with Zod ruling Kandor.
Cut out the whole brooding Supes from For Tomorrow and base the film's first three quarters entirely on Kandor with a Nolan-like twist before the final act and Supes escaping Kandor but with him and Zod facing off on Earth.