There's value in using the "Superman," "Batman," "Bruce Wayne," and "Clark Kent" names in-story, in a similar manner to the League of Extraordinary Gentlemen. Superman could have an "S" logo, especially the Golden Age version. He could have the Golden Age color scheme as well. (It's not like some versions of Robin Hood have to wear orange or some versions of Dracula have to wear white.) And good luck getting money out of an LLC created just to publish such stories. They can fold and the creators can find other means to publish.
I know I'm now particularly interested in the Golden Age versions of Superman, Batman, Wonder Woman, Green Lantern, and Dr. Fate. And in about 15 years, I could "own" stories about these characters, even if I don't own the characters themselves. You could just title your book something like "Ultra Comics Presents The Super Society."
I mean, you could have Wonder Woman set in the 1920s hanging out with the Great Gatsby-- Or Bruce Wayne could meet Sherlock Holmes-- Or Alan Scott and Doc Nelson could meet Doc Savage, King Arthur, Hercule Poirot, Steve Rogers, and Mickey Mouse-- Or Superman could meet Tarzan, Popeye, John Carter, King Kong, and the three stooges. Aquaman could really go to war with Namor over Atlantis. I'm not going to miss out on opportunities like that.