6. Create a “dark gritty” Justice League.
This is the best solution to the problem of having to introduce characters and show why they belong together, all in one movie. There’s no explanation needed, if they’re dark and gritty enough. Everybody instinctively understands “dark and gritty,” and nobody ever wonders what motivates a dark, gritty character. Batman gathers a team that includes Dark Superman (wearing his black Super-suit from The Death of Superman), Dark Wonder Woman (wearing armor, or maybe even pants!), Dark Flash, and Nihilistic Olive-Drab Lantern. Together, they join together to battle the darkness… darkly. The conversations among the group could consist of all of them arguing over who’s more tormented: “Nobody can understand the things I’ve seen.” “Eh. The things you’ve seen are much easier to understand than the things I’ve seen.” “I am the night.” “Well, I ate the night and pooped a total eclipse of the soul.” And so on. Plus they all keep insisting they work alone, but then working together.