Here is how I see it. I initially was going to make a picture of Batman Harley and Damian standing together in family photo style with big, Harley-esuqe words saying BIG HAPPY FAMILY, with Batman in his dark, cloaked and sulking figure and Damien imitating him and Harley hugging Batman while rubbing Damian's hair. It was really cute in my head.
I saw an argument about how Batman's relationships have all been a certain way and that they all end a certain way, but you seemed to have glazed over the obvious: THEY ALL END. Batman may have a certain niche for love-interests, but they all end because of how he is. He finds a girl he knows is strong-willed, as stubborn as he is, and can stand as an equal to him. But the problem is is that Batman himself is too much of a strong willed, stubborn individual that always acts like he has no equal except for Superman and WW (I'll talk about my BatxWW ship some other time).
HArley actually IS strong-willed and and proactive and alot like all the other girls Batman has dated. The difference? Harley isn't cold or dominant, she wants a relationship with a dominant male partner. She knows how Batman thinks and would let him have his ego trips. Let him sulk in the basement and play with his toys. And while he does so, she'll bake him a pie and come down before he gets too emo. She's a therapist, so she can try to help Batman get over his drama. I can imagine Harley having enough with Joker's abuse and go over to Batman, wanting to help him take down the Joker. He doesn't trust her, but after a few misadventures that prevent him from taking her back to Akham, he is convinced by her that she is over the Joker (the only real reason she was a criminal in the first place), so he takes her to the Batcave while he thinks it over. SO over time, Harley's bubbly attitude combined with her practical intelligence and semi-understanding of the joker's mind, Batman begins to respect her as an individual. She starts imposing herself around the house: cooking meals, going to parties with him when he's bruce wayne, and being all around the only thing fun to have happen to batman in a while. Soon Batman starts taking her on missions with him and she dons her own Batgirl outfit, stylizes with her old Harlequin outfit to make it original and the two clean the streets.
@deathbymanga: THat would be awesome. And Harley actually is quite smart, the joker just messed her up. Her criminal psyc skills and being and ex one would be rather helpful to batman. Harley as batgirl would be pretty cool too, man I'd love to see what that would look like lol
Joker would think it's hilarious. Catwoman would get into a catfight with Harley. Harley would try to get off Batman's mask, he'd shut her down, she'd go off on a psychotic streak, join back up with Joker, they'd end up in Arkham, Batman would be the first superhero to mourn his latest girlfriend ending up in an insane asylum.