I'm not sure Muller's needed. During the Martin days, Muller was the "player's friend" assistant, keeping a good cohesion and atmosphere within the group, aside from technical duties.
I think right now the coaches are doing a great job keeping the team happy and the atmosphere light-hearted in the room. Muller isn't really needed. Gallant is effectively doing what he did, and he's doing a great job of it. Too many coaches might just obfuscate the message as far as the technical part of coaching goes.
However, if he were so much willing, Hamilton is a place I would be giddy to see him work his magic at. He is clearly the least of Carolina's problems.