I don’t think they planned it to be about Lily. It’s just another unneeded additional storyline that the writers love to randomly add. Making Lily the Dragon’s daughter would have been a golden opportunity to easily resolve that loose end, but apparently that’s not the case. In regards to actor availability, making the Dragon Mulan’s father is even more questionable, because Jamie Chung is recurring on Gotham this Season. Her character on Gotham is currently inactive, but could resurface later this Season. Needless to say, Agnes Bruckner is likely more available than Jamie Chung is.