1. Button Sequence
Audiences are used to Marvel's end credit scene aka the button sequence, where fans are treated with a taste of things to come. Volume one concludes with a brief exchange between Pandora (introduced at the end of Flashpoint) and Phantom Stranger (two thirds of the Trinity of Sin). Where the reader discovers that Pandora is cursed, and the only way to break it is by imprisoning "The Strange" her plan is to use... "The Justice League whether they like it or not." The source material has already done most of the heavy lifting, and through the use of the current crossover event Trinity War, the first major crossover event since Flashpoint; the Justice League, Justice League of America, and Justice League Dark are all pitted against one another because of the mysterious Pandora. If they could get this movie out by 2015 not only with the collected editions be available for reprint, but they could compete directly with the Avengers.
At this point all they need to do is keep their heads above water, and the expectation has been both set and being raised by the Avengers. I'm all for seeing an original story, but with a story this grand and well suited to follow Man of Steel DC needs to show some faith and respect for the work that has already been done. And as one of the leaders in the comic book industry, with the most recognizable characters, a centurys worth of stories, and characters reinvented for a modern audience it time to start planning and putting these ideas to good use.