I can't vote. I don't like any of those options.
I think a unified timeline could be good for characters who have been struggling because of the frequent reboots destroying their history, but I don't trust current management to craft a decent timeline, and they have already botched it by making Wonder Woman the first hero or reinstating Clark as Superboy but not his Legion membership.
I think replacing all of your main characters at once with nobody-saw-them-coming substitutes is a bad idea. It worked in the 50's because comics featuring Jay, Alan... had stopped coming out several years ago, their fans had quit comics, and the newer kids didn't care about the original GL, Flash...
Now?
It's been a long time since fans quit comics when they outgrew them and were replaced with newer fans.
Replace or retool a character, and their fans will NOT shut up about it. Kara Zor-El fans didn't shut up about it, Hal Jordan's didn't shut up about it, Batgirl Babs' didn't shut up about it, Batgirl Cass' didn't shut up about it, Barry Allen's didn't shut up about it, Wally West's didn't shut up about it...
Replacing Clark, Bruce, Diana, Barry, Hal and Arthur at once is a bad idea, doomed to be short-lived.
I think some comic line set in past continuities sound great, until you realize DC is still being run by people who thought a Jokerized Supergirl, Captain Marvel, Wonder Girl... were a good idea.
Compounding the issue, DiDio, who was spearheading and managing the initiative for better and worse, has been ousted. But it's too late to cancel the new reboot, so now DC will have to rush through a correction course.
There's NO way it'll work out well.
