Thanks to the Suicide Squad and League of Assassins arcs over on Arrow and the names dropped at Arkham Asylum during the Elseworlds crossover, we know that pretty much all of the major names in Batman's rogues gallery are already either dead or in custody. The inference for me at least was, that like Batman, their stories are over and done. I wouldn't mind seeing the likes of the Penguin or the Riddler or Catwoman show up on Batwoman, but I would be equally okay with seeing the show form its own rogues gallery.
I agree; Batwoman/Kate Kane should have her own rogues gallery much like Batman/Terry McGinnis got his.