Batwoman isn't allowed to use Renee Montoya because she's in Birds of Prey, DC still got that embargo going. Really hope Arrow is allowed to bring back Slade, they're allowed to use the identity of Deathstroke (Kane Wolfman, John Digglke Jr), but not Slade. It's weird. Titans can share.
Also Batwoman won't be repeating Arrowverse characters, although who knows how long that'll last. Maggie is out because Supergirl had her, although that was a different universe. Ra's, Nyssa, Talia, Firefly, Deadshot, Anarky are all out. Would be interesting if Solomon Grundy that Arrow teased all the way back in S2 finally returned in Batwoman.
Man, Batwoman is gonna wind up with Batman's sloppy fourths at this rate.