I don't think this has ever been done. What character would be better off in their own universe? This includes moving their villains, sidekicks, settings, etc to this new universe. I feel like this would make sense for a lot of weaker characters who don't seem to fit in with the other people in their universe who are more powerful. Speaking of which, Batma-
Okay nevermind... BATMAN DOESN'T BELONG IN THE DCU!!!
Think about it, he'd make much more sense in his own universe. He's a human vigilante in a universe full of planet busting powerhouses and cosmic beings. It just don't make no sense! Batman would be one of my favorite characters if he, Gotham, and it's numerous psychopaths were separate from the rest of DC. This was done in the Nolan films and look how well they turned out! Do you see my point?
Anyway, who do you think needs or would benefit from having their own universe?
Racob has spoken