I think they could do a number of great character studies focusing on the villains, after the success of Joker. Like:
Lex Luthor
Two-Face
Ra’s Al Ghul
Mister Freeze
Clayface
Man-Bat
I could see these as lower budget horror films. In these, the titular characters wouldn’t necessarily be the protagonists:
Scarecrow
The Trench
Killer Croc
Solomon Grundy
Toyman
The Parasite
For comedy:
Plastic Man
Blue Beetle & Booster Gold
Justice League International
Think “The Raid” or “John Wick:
Green Arrow: Escape from Supermax
Nightwing
Deathstroke
Deadshot
Lobo could be done like this but they’d have to spend a little extra on CGI considering the sci-fi setting.
Catwoman would be a wonderful option for a lower budget heist film
I’m not sure how well New Gods will do in theaters. This may be a better place for that project. Cyborg sadly probably wouldn’t catch on with audiences either. No one really responded to him in JL. If they wanna do a movie, do one there.
I think the time is right for Constantine 2 with Keanu. And use him again for Justice League Dark, also released on HBO Max.
The next time we see Justice League in live action, I have a feeling it’ll be a direct to streaming movie or a live action TV series. I think they could do it justice on HBO Max. A self contained Justice League series with no ties to anything else would be awesome IMO.