Well there is the Fox X-men reboot strategy.
Fox released First Class, which rebooted X-men. They were able to keep some stuff, and move on.
And Marvel has has some soft reboots in the past. We don't see Terrance Howard or Edward Norton running around as super heroes. Edgar Wrights Ant-man never happened.
To make a super hero universe work, everyone's ego but the producers has to be hung up on the coat rack. Why was Batman Forever better than Batman and Robin? probably a lot of egos working against the movie by that time.
Actually the Burton Schumacher anthology is actually something to look at for reboots. They kept on Alfred and Commisioner Gordon, and Robin for the second set, but the villains changed, even batman changed, and it really didn't matter. Not great movies, but the general public were a lot more capable of moving on with new casting at the time.
I think they'll build the new universe with the Aquaman and Peacemaker crew staying and everyone who can't hang or has too much of an ego or wants too much money is going to get recast. I'm not even sure Gal Gadot is gone, but Patty Jenkins may not be meshing.
I think the best thing they can do is Cast Khary Payton as the live action Cyborg and play his theme song.
https://www.youtube.com/watch?v=uR131fc2pZY