So, in case anybody gives a shit, let me say that Justice League should NOT happen, unless they throw out EVERYTHING they've already done (which it looks like they have, so far), and go smaller. Not too small, mind you; this is a team of variously-powered god-like beings, and getting them together will take more than just a team-up of mob guys from Gotham and Intergang from Metropolis to stoke the fires of the superteam.
The following are my suggestions for how to get this whole shebang underway, WITHOUT blowing their load too early with intergalactic villainy or establishing a huge villain team-ups with too many characters. Whether or not they want to establish these heroes individually beforehand, like Marvel did, is moot.
1. Don't Use Darkseid
Darkseid is a great villain. He was created by Jack "King" Kirby, along with the rest of the Fourth World and the New Gods. Having said that, Darkseid is a horrible choice to throw into the mix for your first outing with the Justice League.
This is one of the main reasons the New 52 Relaunch of the Justice League was so terrible. Darkseid can have a polarizing effect on all our do-gooders, sure. But to blow your load with DC Comics' ultimate otherworldly baddie right out of the gate? Dumb. Fucking idiotically dumb, really. It's how I felt about using Parallax in Green Lantern: the reason Parallax was so powerful in the comics-- and why his retcon into being the living embodiment of fear that possessed Hal Jordan was so well-received-- was because it was a retcon that fit and redeemed a character who was pretty fucked over to begin with thanks to trends in the nineties. Parallax was an ok movie monster, but to undermine his importance to the current mythos and introduce him to moviegoers who don't give a flying fuck about comics was weak. Darkseid would face a similar problem. Most folks don't know who he is, and he would come off as pretty generic with no buildup to how much of a badass he is. Take into account that Darkseid is very similar to Marvel's Thanos, and you would merely confuse your audience and make them think you're ripping Marvel off, when they get to Thanos in the inevitable Avengers sequel(s).
Darkseid is a character that you need to build up to make a believable threat. If you were to use him right away, and your heroes somehow came together, never knowing each other before a 2, 2 1/2 hour runtime to defeat him, it would come off as forced and anticlimactic, at best. Ya know, just like that sixth issue of the New 52 Justice League. And story incongruousness aside, where the fuck would you go from there? Being the Baddest of the Bad amongst DC villainy, what would you do for a sequel, if your movie is successful?
There are plenty of other villains in DC's long history to play around with on screen. If you're going to use Darkseid, don't do it first. You risk putting the cart in front of the horse that way. Slowly build toward him, if you absolutely HAVE to use him, like they're doing with Thanos. Otherwise, let's leave him out of the equation, shall we?
2. Don't Use Joe Levitt As Batman
If you have any fucking sense at all, Warner Bros., you will keep Justice League's version of Batman far, far, FAR away from Christopher Nolan's vision of the Dark Knight. I understand that you want a familiar face for your audience, and I'm sure JGL would do great as the Caped Crusader, but here's the thing: this is Goddamned BATMAN we're talking about. Other than Superman and Spider-man, Batman is the most recognizable superhero in THE WORLD. We all know who he is and what his fucking deal is. Do not waste your money or your moviegoers time with re-establishing Batman's deal in this movie. Cast someone with the stature and physicality and whose chin looks flattering poking out of that cowl, and just give us fucking Batman kicking ass in Gotham and discovering the pending crisis that will bring our heroes together has come to his doorstep. Batman should be the first to catch on to whatever is going on and a reluctant participant in the team effort to stop it. We don't need to see Bruce Wayne in this movie at all, you hear? BATMAN is important to the Justice League, and the actor portraying him should not be seen without the mask, period.
3. Have A Decent Script
This should go without saying, but the fact that this project in various iterations has been floundering since AT LEAST 2007 does not instill confidence. You have to make sure the script is decent before you do ANYTHING else. No green-light, no casting, no costuming, no storyboards, NOTHING should be done until you have a script that isn't complete and utter shit.
There are plenty of (good) stories about the League's formation that a halfway decent scriptwriter can look at for inspiration that don't involve fucking Darkseid or our heroes acting like complete assholes (well, except Batman. Batman is allowed to be a dick, at least at first).
My suggestion? When JLA was launched in the late 90's, a version of Starro the Conquerer was used that had facehugger-like drones to enslave Earth's population. Something like this would be a great way to get the team together, without relying on an Apokalyptik threat like Darkseid.
Perhaps it would be best to show that Superman and Batman already know each other, or the camaraderie between Flash and Green Lantern. We don't have to show everyone meeting for the first time; history can be easily explained with several lines of dialogue. You'll save time building character relationships by showing that some team members already have friendships, or at least have met in the past. Even if you use only five characters, as the most recent reports said, you're going to have one hell of a time giving everyone something to do (let alone developing characters) without solo movies to establish figures like Wonder Woman, Aquaman and the Flash. So go light with the exposition on Superman and Batman, and have fun with the down-to-earth Flash and the culturally inept Aquaman and Wonder Woman. Don't beat us over the head with Supes and Bats shenanigans; your audience already knows who they are, and so should the characters in your movie. If you're going to do this shit backwards (i.e. the reverse of Marvel's model), give the other characters time to shine to drive up interest in the solo movies that can follow Justice League.
Oh, and please, for the love of Kirby, try to steer clear of those
4. Don't Try To Copy Marvel
I know you soulless corporate bastards want that Avengers money so bad you can taste it. But if you want to make money on it, you can't cheapen this brand or these characters in order to make a buck. I know you want to make money. But establishing this brand, in a unique way, entertainingly and successfully, will mean that you can CONTINUE to make money on sequels, merchandise and spin-offs. Does Marvel have a plan to successfully continue their characters between and beyond Avengers? Absolutely. But that is what's working for THEM, for THEIR characters. Trying to emulate Marvel's business model will further cheapen your brand, and your audience will know it. They'll see Justice League, a movie based on one of the original superhero teams, and dismiss it as an Avengers ripoff almost immediately. You need someone who WANTS to make this into a movie, someone who, first and foremost, has a love and an understanding of what makes these characters tick, what makes them special. Making money and following your studio notes about why such-and-such doing such-and-such isn't marketable and being your paid bitch should not be qualities to look for in a writer or director. Story and character should come first to whomever you hire, and if it's good, like Whedon's Avengers, it will sell. Slavishly trying to replicate Marvel's success is going to look like a slavish replication of what Marvel has done, period.
If you make Justice League first, then make it able to stand on its own before licking your lips at all the money you can make on what comes after. Drop all the references and hints that you want, but adding those instead of story, dialogue and character development will not hold your movie together. You can ask Angela Bassett how well that Amanda Waller cameo worked out for her and get back to me, if need be.
Conclusion
If this movie ever gets off the ground, they'll probably fuck it up anyway. I think weighing in my two cents is probably not going to go anywhere except to (possibly) ingratiate myself with my fellow dorks. Even though I have strong opinions about what I would like to see done with this franchise, I can't imagine how insurmountable a task this must seem to any writer or director approached with the job. But at the same time, is it truly that difficult to make a film based on a long-beloved property that doesn't change things to piss off the fans and still have universal appeal? This is the Justice League, for fuck's sake! Almost everyone knows who Batman, Superman and Wonder Woman are! Let's leave the exposition for the comics that spawned this media and merchandising machine that the WB constantly profits from, and just make a damn fine movie to rival Avengers in scope and scale without tirelessly trying to top it, ape it, or outsell it, shall we?
Just give us a good, un-rushed Justice League, Warner Bros. Us geeks will continue to sort out which superheroes from which universes would win in a fight while you and Disney have your pissing contests over how big the box office is.
-Swift