Ever since the news broke out that the multiverse might help set up a DC movie and TV crossover, DC fans have been going crazy, coming up with insane theories that they hope will come true. I am one of those "fanboys" who conjured up a crazy theory that just might work. Remember, this is my theory, so if you feel like something should be changed or added, feel free to leave it in the comments. Now, onto the theory.
The first (and most obvious) universe is the main DC Cinematic Universe. This universe consists of Batman, Superman, Wonder Woman, Aquaman, Green Lantern, Cyborg and the Flash. This universe would be the one that all the other universes travel to. As far as we know, each of these characters will get their own movie which could help expand the universe to places such as Themyscira and Atlantis.
The next universe is the TV universe. This universe is already pretty well established, but a few more characters wouldn't hurt. They already have Green Arrow, Flash, Black Canary and Huntress. This list doesn't include the characters that DC are planning to bring to the small screen as superheroes, such as Atom and Wildcat. The TV team could make up the Justice League of America similar to the one in the New 52. This universe would be the hardest to transition into the movie universe because TV actors may be shadowed and the universe is grounded and more realistic, but I will expand on that later.
The third, and final, universe I think should be part of the multiverse is the New Line universe. DC announced that 'Shazam' will be made by New Line Cinemas, meaning 'Shazam' may exist in a different universe to the one with the main Justice League. It was also reported that DC may be doing this universe when they said 'Sandman' may be a 'New Line Universe'. Guillermo Del Toro recently finished his Justice League Dark script which may play a big part in the New Line universe. This universe could show the magic side of DC through characters like Constantine and Zatanna.
How it can be pulled off
I think that the movies that feature this crossover should be based on the 'Crisis on Infinite Earths' storyline. It should first occur in a Justice League movie, but instead of using the anti-monitor, Darkseid should be the primary villain. I would use Darkseid because he is a much bigger character and would be more memorable as a live action character.
I would not only use one Justice League movie, though. It should be split up into two parts with several spin off movies in the middle of those movies. It would properly represent a major event in the comics. Not only will the events be shown in the movies, but in the TV universe as well. I don't think DC should dedicate a whole season to the event, but a miniseries that features the TV characters plus some of the movie characters.
As I mentioned before, the TV universe would be the hardest to translate into the movies. This is because the TV actors may not be as good as the movie actors and the grounded feel of the shows would be completely lost. This is almost fixing itself. Arrow is bringing superpowers into the show slowly and The Flash is already there. As for the acting, I believe that the TV actors such as Stephen Amell and Grant Gustin are already solid actors who could hold their own against Hollywood heavyweights like Ben Affleck.
As for deaths, I think the TV Barry Allen and the movie Green Lantern should be the ones to perish. They would both affect their respective universes dramatically and could open up so many storylines that they could explore. In the TV universe, there would need to be a replacement flash like Wally West and in the movie universe, a new Green Lantern could have his own movie (preferably Kyle Rayner). That's not even mentioning all the mourning of the other heroes.
There it is, my DC multiverse theory. Thank you for reading. This is my first article so please leave some feedback and maybe some suggestions of what I should write about next.