I don't think it's a hard sell to create new and original characters, that will ultimately be successful. I don't think the suits want to put the resources and dollars behind it though, to the point they're rarely creating new characters at all...heroes or villains. It's easy to throw an established brand on a "new" character, and push them to the point you think they're successful. They've also had more "legacy' characters that failed than new characters. But also, the creators tend to want to save their new characters for their own imprints.
And Duke Thomas would probably be the last for DC. He's not really legacy.