Ellis Wyatt. I think he would be perfect.

Man..... That's a tough question. I feel like I'm not going to be able to sleep till I answer it.

Not sure how his acting chops are since I'm only familiar with his comedic roles. So, unless you're sure he'd be able to handle a meaty role, a couple of obvious cameos (depending on whether the characters are in the script) would be Hugh Akston or Jeff Allen (train stowaway). A bunch of antagonist roles also come to mind ... Wesley Mouch, Dr's Ferris or Stadler.

I think the producers will want to find the right actor for each role, rather than picking an actor and then trying to find a role for him (or her).