Should they just soft reboot the Justice League like they will the Suicide Squad?
I think it's kind of a shame to not try another JL movie just because the first one bombed. And it's not like the team is broken storywise, only in terms of tone, IMO.
I think they could get away with some recasts after the Flash movie and just have a new JL series where the team is already together and more developed (no need to go into Mother Box crap again).
I'd adapt Morrison's first arc and introduce Martian Manhunter, Hawkwoman and John Stewart.