Mind you trannies is itself a derogatory word.Good question. I'd have no issue myself referring to trannies as auld dolls but I'd like to know if they would be ok with it.
I remember years ago this auld doll from Sligo went mental when I used the term "auld doll" to refer to a woman. She thought it was very sexist. Thankfully a Cork auld doll stood up for me and just mentioned that's it's inoffensive cork slang for a woman and that her boyfriend refers to her as "my auld doll"