Roger Daltrey has made it very clear that he will handpick the actor, and he has a specific requirement to choose him.
For the Keith Moon biopic, Daltrey says it's all in the eyes.
In a recent interview with the BBC, Daltrey said the following:
“It’s going to be very, very dependent on the actor and the actor’s eyes. Because you’ve got to cast it completely from the eyes because Moon had extraordinary eyes.”
He also noted that the story will focus on more of his "outlandish" behavior, rather than avoid it, which honestly is the best way to go about a documentary/movie: Keep it real.
You can listen to the interview here.