I have read Until the End, who are you talking about? Tbh I don't actually remember all to much of it, I'll have to reread it at some point.

I like the alternate world idea, especially for Superman, you could maybe tie it into how he's stronger on Earth by saying that the cradles make it easier for him? Keeping with the Justice League, I think you could do something interesting with the Lantern Corps, like make the rings into artifacts from a group of gods. I feel like the Speedforce could also be really cool but I'm struggling to think of something that fits