I was so happy they featured her in Soul of the Dragon even if it was for, like, two minutes .It would be cool to see Black Mask on the series, since I feel he was unfortunately overlooked on BTAS. And what the heck, let's see Silver St. Cloud, too.
I don't particularly want to see more recent Bat-villains like Hush, Zsasz, or Professor Pyg show up, though, as none of them do anything for me.