I'm actually pretty psyched about this and wish I could go see it. I saw The D (The Greatest Band In The World) cover Heaven On Their Minds a few years ago live and it OWNED. In a concert setting I think Black would be a perfect Judas, but in a concert setting only. I would love to see him play Herod in a full production. There was a clip from Mr. Show on youtube, and I can't find it now, of a full JCS parody. Seek that out if you have any doubts.
As far as Freddy? Eh I don't know. He would have to be sat on or it could get out of hand, even though he could handle the comedy perfectly. Maybe if they make DRS, the musical, into a film. Then he could do Freddy.
I got rid of my teeth at a young age because... I'm straight. Teeth are for gay people. That's why fairies come and get them