The YJ4 got so screwed up by N52 that I wouldn't mind a near-complete reboot of them in YJ Rebirth.
First and foremost, each of them needs to be reconnected to their JL counterparts. I know that YJ hung out on their own and apart from the JL in their original incarnation; but that was back when their ties to the League were unquestioned. I prefer the“trainee team” concept from the TV series this time around because it gives the kids ample justification to interact with their mentors and to establish and deepen ties to them. So have them hang out in JL headquarters, with various JLers supervising them. See how things go after about a year; and if everything's going well, then let them strike out on their own.
For Tim, I'd bring his parents back into the picture and have Tim move back in with them. Bring back Ives, too: Tim needed to reconnect to ordinary life instead of being immersed in the superhero world 24/7.
Cassie could get a revised origin as part of what Wonder Woman Rebirth is doing. Make her less of a thief and more of a headstrong and slightly nerdy teen.
Bar-Torr needs to be revealed to be Inertia; and Bart Allen needs to be introduced as a new teen hero, claiming to be Barry's grandson from the 31st century. Don't worry that Barry isn't anywhere close to having a fiancee at this point, let alone a wife, children, or grandchildren; as long as the Flash title doesn't do something inane like killing off Iris, they can easily manage it.
Kon El should be revealed as a reconstruction of the N52 Superman, a “Cadmus clone” as it were. Re-establish Tana Moon, Dubblix, and the project.
Steal Jackson Hyde away from the Teen Titans, and do more with Mia Dearden.