Time has not been kind to The Killing Joke. There's been a ton of discourse over how badly Barbara Gordon was treated/written, not to mention how readers misunderstood The Joker's unreliable narrator schtick and actually bought his sad clown act. However, I argue that The Joker could have done something much worse to Barbara, Commissioner Gordon, and Batman without resorting to sexual assault.

He could have told Gordon that Barbara was Batgirl.

Picture this: The Joker just murdered Jason Todd. Batman, wracked with guilt and anger, dismisses Barbara out of fear she may be killed too. Barbara doesn't take this well, and she still gets attacked/hospitalized by The Joker, but not sexually. However, The Joker finds out she's Batgirl, and then kidnaps Gordon. Cue most of The Killing Joke, only instead of showing Gordon some unwholesome nude pics The Joker tells him his daughter was Batgirl. This doesn't break Gordon, but it ruins his relationship with Batman. He will hunt Batman down when this is over, and will never see him as being different from The Joker, Two-Face, or any other costumed baddies in Gotham.

Anyway, then Batman shows up. He and The Joker fight, Batman wins, and he comes close to killing The Joker, but stops himself. However, The Joker still wins. Batman is now a liar in Jim Gordon's eyes, and now Bruce no longer has the police on his side. What's more, with Barbara out of the picture Bruce is more alone than ever. More importantly, The Joker gets to call Bruce a liar and a hypocrite, just like he is. And by sewing that seed of doubt, The Joker sets the stage for one of several possible scenarios:

1. He gets Batman to kill. Not ideal for The Joker, but at least he gets to be immortalized as Bruce's first victim.
2. Batman quits. I imagine something like this was behind the plot of The Dark Knight returns.
3. Bruce gets found out and goes to jail. The Joker becomes the man who broke the bat, and is revered by Gotham's underworld.

Granted, none of these ideas completely fix The Killing Joke, especially not for fans of Barbara Gordon. But at least this way people wouldn't misinterpret The Joker as an epic sad boy with no real plan, and The Killing Joke as a whole would feel like a bigger, more nuanced story.

Also Batman wouldn't fuck Batgirl, which would be nice.