I am sure there are ways, and following the new JLA would be a good idea, see how they do it. Never thought about that.
But the problem I see is that on all the cartoons that Darksied has been on, or TV shows like Smallville, he is the ULTIMATE evil. Like the devil or something.
And in all those shows when he is introduced he doesn't go away. He was brought up in Superman and kept returning until he was forced to leave by the New Gods. And in JLA he didn't leave once he was brought up again until he was killed in an explosion that destroyed a whole solar system or something.
He just seems like a villain who, once introduced, you can't forget about or put off to the side until he is defeated completely.
Maybe I am wrong, but he seems like a bad guy who you introduce in movie 1 and is the bad guy in 2 and 3, and FINALLY defeated in movie 4... finally.
It would be smart to introduce him in a JLA movie so that he can be used to help launch a New Gods movie, but I am not sure how.
In the comics it wasn't him but his forces that were introduced in Jimmy Olsen. But then its like Smallville again, you never see Darkseid he is just mentioned over and over. He deserves to be in a movie, and if he is used in a movie it should be him...
I am just sort of speaking out loud, rambling out ideas...
Thats why I suggested Mongul though. I can easily see him introduced as a HUGE threat to Earth and able to defeat Superman in hand to hand combat. But in the end is totally defeated and humiliated by the JLA, "his unconscious body tossed at his enemies" defeated, in JLA movie 1. He could even use Starros to build armies of humans or something. He also has those plants that make people see dreams.
Then again
I also like the idea of the White Martians.
Like in the JLA comic in the 90s, I think it was, where they pretended to be a team of Superheroes who was going to save Earth and make it a Utopian society. Secretly they are taking it over. It could take the formation of the JLA, a real team of heroes, to defeat the White Martians.
You get the reason Martian Manhunter is there, maybe he is what brings them all together. You get the scene where Batman is shown to be not just a human without powers but the most dangerous human when he shows he figured out the White Martians weakness and takes down three of them.
We also get the scene where the JLA have to address the public to assure them of their safety (I think the White Martians were going to execute the JLA members live to show the public all hope was lost) and the JLA choose Superman to talk to the world because he is the most trusted superhero.
In the address he could tell the public that the heroes are going to protect them, by banding together and forming the JLA.
Just an idea. Rework that storyline into a movie.