Please let Cameron Monaghan play the true joker in the next crossover. You'e already opened the jack in the box. And you're likely already going to have mutiple live action jokers anyway with Phoenix and whoever might plays him in the Robert Pattison version if that's not phoenix.
Miller comes across well here, his Justice League film was a flop with critics, underwhelmed at the Box office and his Flash was often compared unfavorably to the longer TV one, but he wasn't petty about it and agrees to even a small appearance on the CW. Good sport.