Eivion

A Beyond line would be perfectly fine as long as they don't make it too big. I don't see much reason to add anything else right now other than a JLU Beyond and the upcoming Superman Beyond. Really its somewhat of a moot point seeing that the Superman Beyond #0 is only testing the waters. Its best to wait and see how that does before wondering if a Beyond line would be a good idea. Personally though, I would love to see one as love the universe and am curious to see what old and new heroes/villains are running around outside of Gotham.

"What happened to Wonder Woman, the Flash, Superboy, Martian Manhunter, Supergirl, the Teen Titans and all their villains? "
"Is Gorilla Grodd still alive? Has Deathstroke managed to elude the grim reaper? "

Batman Beyond is based on the DCAU. Even this current version with mainstream elements it adds is still supposed to be based more off the DCAU than DCU.  Wonder Woman is still around though we never saw her due to whatever embargo was on her in the cartoons. Supergirl left to join the Legion in the future.  Superboy never existed though they could always retcon him in considering how many years later the universe occurs. A good chunk of villains died when Darkseid came back to life at the end of Justice League Unlimited. Gorilla Grodd is dead, ejected into the vacuum of space right before Darkseid comes back.  Due to an episode of Static we know the Titans existed though we never saw them. Don't know if Deathstroke ever existed at all since he was never in any show.