The Question (Vic Sage)- The movie could be really zen like the 80s series. Make it R-rated. Have Richard Dragon, Myra, ect. Mainstream audiences might think Rorsach knock off. Maybe Mel Gibson if they go for an older Vic Sage.
I think part of it is that Harley is attracted to extreme personalities, Ivy, Joker, Riddler, ect. She could try to start over, and get a normal job, but eventually that chicks gonna want to hop in a car with "Mr. J" and gas the city.