Also if you want to add any side characters or powerful items that’s good
Lineup: Superman, Batman, WW, The Flash, Cyborg, Aquaman, Martian Manhunter Villain: Darkseid or tLoD
I think for me it would be the og 6
Green Lantern (probably Hal)
I think I’d add Fire and Ice because they normally wouldn’t get any attention and you can introduce them to the mainstream audience
The threat would be the Legion of Doom
(Sometimes I think I have way too much time on my hands)
Following from the first movie, I’d include the original lineup plus Green Lantern (either Hal or John) and probably add Hawkgirl as well, a la JL animated series. It would help to diversify the group more, plus they could introduce her as a way of giving the DCEU more of a cosmic presence. Thanagar could play a part later in the movies, maybe being a focus in a Green Lantern film or Hawkgirl stand-alone.
I really want to see a team up of villains, especially since we saw that teaser at the end of JL. Lex and Deathstroke, of course. Don’t know who else they could include, but Lex already realizes he needs help since now the heroes are teaming up.