Why have i never heard of this idea? Superman lives far off in the future. Everyone he knows is dead. So, he's a sort of an intergalactic Ronin. Just like these wandering heroes like 'The Man with no name' or Yojimbo. He goes from planet to planet instead of town to town and sets things right before moving on. Oh and make him a legendary hero. No one knows whether Superman is alive or dead. And he keeps it like that. (Some people just don't change).
It would be a very costly show, now that i think of it. Lol.
Edit: I want to add a few words. Its kind of surprising that whenever people want to write out of continuity Superman stories they write origins.