"I doubt Cats and MrJ would get along well in a gang bang anyway."
Honestly, I doubt anyone would get along in that Gang-bang. Maybe without The Joker around.
Honestly, I never got the idea of Bats/Joker slash. Maybe on Joker's end, but Bruce would have none of that shit. There's mingling with a criminal with some semblance of a moral code (i.e. Catwoman), it's entirely different when it comes to an amoral sociopath. He'd definately be an, ahem, "unwilling participant" in that situation. IMHO, of course.