How about some side-Elseworlds. Things like The Nail where the change might have involved one of the Big Two (Batman/Superman) but the story being told focuses on other heroes.
We saw Batman and Diana plus Green Lantern in Red Son, but imagine J'onn in that world. Not only is he a "stranger in a strange land" but this America associated powerful aliens with the Soviet dictatorship.
How would the Holy Terror world deal with Diana? Or Shazam?
What would the Golden Age be like in a world where Superman dies War of the Worlds"?
What would other heroes be like in the same universe as Gotham by Gaslight?