This basically confirms that: Warner Bros gave Gotham City Sirens to David Ayer and pitched a harley/joker movie, but Margot said no to both of them and started developing her own Birds of Prey movie instead.
He felt for the
first time, as an actor, that he was like “I’m untouchable. Every
scene I do with any other actor, it doesn’t matter how amazing they
are. I’m controlling and leading these scenes.” He was so confident,
and he was so proud of that role. He was really excited for that
film to come out. He was… it was the first time I’d heard him in a
long time being excited about, like, “this role I’ve nailed it.” -