I mean it's too late now but I think James Gunn should've announced the end of the current DCEU instead of trying be all coy about it and announced a big finale movie that would wrap up the current universe. It would of course be animated but at least it would bring some closure. All of the unreleased movies would play a role in building up to said movie. This would make it so they could bring back just about everyone as voice actors and anyone who they weren't able to bring back for whatever reason, they could just recast. They could also end it with a glimpse through the multiverse that ended on a new Earth that would be the upcoming DCU.