I'm only in the middle of Rough Beasts of Empire, but at this stage, I could very conceivably envision characters such as Sisko, Kira, and the DS9 characters aboard Aventine (Dax, Bowers, Leishman, and Dr. Tarses) showing up in future DS9 stories as supporting characters, much like the way that Janeway, Seven, and The Doctor showed up in the pre-Full Circle Voyager relaunch novels, which means that if you keep Quark, Ro, and Julian as main characters, you're only dealing with introducing between 5 or 6 new characters, which is only between 1 to 2 more new characters than were introduced in Avatar (4).