The Muller idea actually really intrigues me. He's worked with some good coaches as an assistant, he was saddled with a pretty bad team in Carolina and it appears he's well respected around the league. I think he went back to Montreal believing he'd have an opportunity for a larger role than he had in St. Louis, but with Julien there, he might be looking.
Muller has a reputation for developing good power plays, he never took a shift off as a player, and as an elite young forward in his own time, he might be a good influence for Seguin, Benn, and the glut of other young players coming through the system. It might be a bonus that he had played in Dallas too.
Beyond that, Gerard Gallant is an interesting name. I thought Ken Hitchcock was retiring, but he might be willing to go somewhere on a short-term deal. Kevin Dineen appears to be a favourite for a lot of positions, too. One wonders about Ralph Krueger too.
One suggestion I read somewhere that may be a bit out of left field is Phil Housley. He succeeded as a head coach in the world juniors and has developed some good young defencemen in Nashville while working under two highly esteemed, yet very different coaches in Barry Trotz and Peter Laviolette. Also, Nill would be quite familiar with his work with USA Hockey as he lived close to Ann Arbor and spent a lot of time around that program when Housley would have been there.