In Gunn we trust.
I just want a quick 3-4 films of solid action and pace, focus on the principle characters, then tap into all those TV shows to flesh out the roster. KC is yet another "flip the script" story that banks on readers being very familiar with all the backstory in order for it to really hit, but if they try to recreate it all from scratch, KNOWING they will have all these folks walk away or go bad or whatever, I don't think the writers can successfully hide their hand for long nor will audiences will buy it. We HAVE dozens of DC films in the collective memory bank already, we don't need 5 films each setting up yet another actor as superman, batman, wonder woman, etc. Just reset the backdrop, introduce the current line up, and get to it. If they think they can do another "20 films to Endgame" stunt, I gots baaaaaaad news for them.
Shit, they should just cast Starr as Homelander in lieu of Magog market it as a The Boys film, and have the Justice League show up mid reel out of the blue. THAT would put asses in seats, no question!!
I think you’re overthinking this. With how old the characters are in the Kingdom Come comic, they could do several Chapters (what will basically be their MCU-like Phases) and wrap it up…and then a good deal amount of years later bring a bunch of the cast back for a surprise final film: Kingdom Come. And they don’t even require a ton of them, really only Superman, Batman, Wonder Woman, Shazam, and Lex Luthor‘s actors as the other DC characters aren’t focused on much in the story besides them (hell, IIRC they don’t even clarify who The Flash is at this point, whether it’s Jay, Barry, Wally, or someone else). Okay, and The Spectre, but he wouldn’t even need to appear in a film prior, the movie could quickly explain who he is to non-readers.
I doubt they will “build” to Kingdom Come. Rather, by the time they could even do it, the pieces would just be there naturally and enough time will have passed since the “finale” that the movie can say, “and afterwards, Joker did this awful thing, and Magog came in, etc.
I’m sure there will be big events/villains they build to (Darkseid, Anti-Monitor, Legion of Doom, the Sinestro Corps, Trigon, etc.) but that’s fine as the prior films didn’t for any of that except some build up to Darkseid (for the new verse, I would just subtly build up Darkseid/Apokolips in the background to pay off later, but don’t waste a whole JL film on them fighting one of his minions). And there’s still a ton of characters that would need to be properly introduced who haven’t on the big screen prior: Supergirl (we’re not counting that 80’s film), the Robins and Batgirls (again, not counting those 90’s films), Green Arrow, Black Canary, Teen Titans, Zatanna, Martian Manhunter, Vixen, Atom, Booster Gold, etc. The DCEU and the Supes/Bats films prior to it did introduce viewers to a good chuck of DC’s roster but far from all of them.
But I think for the Justice League film, they probably won’t bother with a solo Flash or Aquaman project prior (but certainly Flash at least will get films after that, we haven’t even had one Flash villain yet on the big screen except Boomerang who was only in the Suicide Squads) since the audience knows them already. Superman film, Batman film, and Wonder Woman film and then boom Justice League film (with also prior to that Lanterns show setting up them, and the Authority, Supergirl, Teen Titans, and Swamp Thing movie each more focused on introducing them and expanding the world and genre possibilities).