Having just seen the show, I wondered about the injury potential in the choreography. It's not just that it's so much dance, the leaping up and off and landing must take a toll on knees. I wasn't prepared for the intensity of the movement, which is almost non-stop, to quote the show itself. I bet two-show days are brutal, and that the company orthopaedist is used.
Rannells seems like a logical choice, with the vocal chops and the {what Namo said} thing. This may also the direction casting the role goes in the future, to someone known in the theater who can carry it for 3-6 months. It's about 15 minutes of stage time, every minute a delicious morsel. And it makes an easy put-in, with none of the cast required except for a 1-2 minute sequence in act two. He's also in the ending choral work, but has no lines assigned in the libretto.
"I'm a comedian, but in my spare time, things bother me." Garry Shandling