Something that has been a recurrence with Joker in the comics is that when he goes sane or when something happens to him he shows remorse for his actions. There have also been times Batman and others have gone into his mind and have seen some for of good in him I think this happened when Specter came after him The Martian Man Hunter went into his mind or something that being said do you think Joker himself should at one point show humanity? I've always felt that if written right Joker showing some humanity might make him even more terrifying. Like maybe it could come out his pregnant wife/fiance from the Killing Joke is alive and raising their kid in secret and he could abduct them and claim he was trying to put his family back together all the while it's evident he's trying to force things and Joker is just completely blind to the horror of his actions alternatively the fiance he had when he went sane (not sure if that story is canon though) could be used in the same capacity.

Either way I'd like a story where Batman isn't so much as Joker's objective or center of his attention but rather Joker treats Batman as more of an obstacle and a annoyance. I like the idea of Joker kidnapping an ex of his and his kid while trying to force a happy ending of sorts because I think it really fits him and I definitely would not want Harley to be the woman in the scenario because Joker kidnapping his ex and kid would be very reflective towards his abusive nature and it would just fit so much if he treated his ex wife/fiance better than Harley even if him being possessive was his sole motivation him treating his ex better than Harley would make a lot of sense.

It would also be nice to see an ex of Joker's that sees him for what he is and calls him out on it because Harley will always go back to Joker and really Joker doesn't give a dam about Harley but ultimately I just don't ever really see Harley as a female character that should be written in a positive light to be frank I've always felt Harley should be cautionary tale of what happens to victims of abuse that don't leave and to be honest I've always pictured her dying at Joker's hands only to tragically realize in her last moments she means nothing to him. All that being said it would be interesting if it was shown even that even if Joker could love he was still just all around bad.

Ultimately I just like the idea of Joker looking for his ex and kid and because it's so personal he just shows a whole knew level of rage and terror like he manages to find his wife and kid, they escape and Harley is the unfortunate soul that has to tell him and he just goes off on Harley in way he never has maybe like this and I can just picture Joker going off on Harley like this.