My very FIRST pitch at DC had a transvestite Black Canary as a main character. It would have been awesome.
Sadly, the rest of the pitch was shit, it was just a terrible plot, and my wonderful editor rightly asked me to start again, and that’s where Savant and Creote came from.
I have no reason why there couldn’t be a trans Batgirl, it has certainly been something I have pitched as a story.