Design your own multiverse
Presuming you can have several different continuities - maybe they are like earth 1 and earth 2 with occasional crossovers, or maybe they are very separate and should never meet. For the sake of this argument, presume that all the titles you want from every universe will get published and have loving attention from good writers and artists. Basically, this is your ideal.
You can go with the same character appearing in multiple universes or each character existing in only one universe.
DC universe #1 would be the JSA. I don't care for characters appearing in two universes, though, so it would not have Batman, Superman, WW or Black Canary, Heroes only get old enough for their kids to make it to about 20. Starts in 1930s or 1940s, since a lot of people won't accept JSA without WWII. New characters may be created, too.
DC universe #2 is most heavily based on bronze-age-through-current DC verse, but not entirely, as some characters merged in at post-COIE would be absent and the Hawks would be more silver/bronze age rather than newer versions.
For me there is some splitting up among different publishers. But not entirely. I'm inclined to have Blue Beetle in DC universe #2 with Batman and Booster Gold and other silver-age-and-later DC characters because the Booster/Beetle friendship is really popular, and I like the idea of Fire and Ice and Guy, even though I don't like the humor of that particular JL series. However, I've also considered that JL version as DC universe #3, without Batman or Superman existing. Not sure how I'd build it, though (who would be the first hero, etc.). And who else should move with them? Martian Manhunter? What about some other heroes that were never on that team? Would Vibe or Red Tornado or Phantom Stranger or Blue Devil or Doctor Light or another one of the Global Guardians fit there? I guess there probably isn't much need to split them off?
Fawcett universe - some things would be changed, like not having Freddy and Mary fighting Sivana's kids. I'd like it to be treated like a continuity where Billy, etc. got to grow and change as others did in bronze age, but are still good kids without the brat-aspect of New52. Possibly go low-to-no time progression, though, since Billy is my big hero of the universe, and his gimmick is being a kid who turns into a grown hero. Maybe ages 12-17 for him. Uncertain what era to set it in.
Vertigo universe would be separate from DC. Characters do not appear in both.
Milestone universe - pretty much what it was when it was published. I think it probably moves to the present fairly easily, though in particular there has been an increase social acceptability of homosexuality and that could have some impact on certain story lines.
