I think Harley Quinn could be a great character in the batman sequels because her relationship with the Joker (as his equally psychotic girlfriend) is funny and bizarre.
It would be more interesting than another boring bruce wayne love interest that ends so predictabally. Instead why not focus on Harley and Joker.
I see them like the couple in natural born killers with a little of bonnie and clyde too.
Her jester suit isn't anymore ludacris looking than the Joker's is.
They should both share the same sick sense of humour and really enjoy messing with batman.
BRITTANY MURPHY FOR HARLEY!