I have to disagree. I would love to see harley Quinn reinvented in Nolan's world but it just wont work becuz Nolan has established this Joker to be completely interested in making merry with anarchy and i don't think the Ledger Joker would be capable of having some affection towards another. On the flipside, you could present the joker and harley as a Sid and nancy relationship where he ultimately kills her by the end.