2. Borrow, Nay Steal, from "New Frontier"
If you haven't read Darwyn Cooke's "Justice League: The New Frontier" or seen the animated adaptation, then you're missing out on one of, if not the greatest Justice League story that's been written. If you've noticed some of these points sharing common ground throughout, it's because Darwyn Cooke did the most masterful job at bringing together the Justice League with common sense and in practical ways that culminated in a grandiose final battle against a global threat. Even the animated version managed to accomplish a lot of this important story in only 75 minutes. The lesson to be learned from New Frontier is, it did it the most right. It serves as an origin story for both Green Lantern and Martian Manhunter, has an evolving Batman, Flash utilized to his fullest, and a great relationship between Superman and Wonder Woman. There's also a lot of smaller core members who get plenty of page time as well like the Atom. (A personal favorite.) But where the story was most accomplished was in its incredible themes. It was actually about something outside of "Go, fight, win!" It drew story and emotions from American history, dealing with the Korean War, the new Kennedy Administration, and Communism. This isn't to say we need a period piece JL film, but it proves how important themes are to the film and how it makes it more practical and easier to relate to. Though we're expecting and desiring a lot of spectacle, the film needs, more than anything else, oodles and oodles of heart. What's moving about the Justice League is that, when they're well written, they feel real, you feel safe because they're around. Of course they're not, but it doesn't hurt to have fiction done so well as to feel real. When we leave the theater after the credits roll we want to feel as if we went on every step of that journey with each of these characters. That's what New Frontier helped do and what the movie needs to both set it apart from the Avengers and make it successful.