Just some random thoughts ...
Coacing options:
Keep Montgomery throughout the season and part ways at season's end. Who knows how the team would respond ... it could be painful if present course continues.
Three alternatives:
Promote Sacco
Promote Leach
Go with someone outside the organization, like Sullivan if he is released by Pittsburgh; or some other candidate.
Really, who is available that would want to step into this mess without a prolonged contract?
I just don't think Pittsburgh will part ways with Sullivan mid-season, which means Boston would have to wait until the off season. There may be additional options ( Recchi ? ) at that time any of which would have to be evaluated at that point.
I would only promote Sacco as strictly an interm with him either released or reassigned at season's end. Or ...
My preference of "in house" choices:
Promote Leach now (or season end depending on other options), but release Montgomery and Chris Kelly immediately / Sacco released or reassigned season's end, but stays for now as a coach.
If Leach is made coach bring in assistants - Adam McQuaid and (Mark Recchi - added at season's end). Sacco can stay until then.
McQuaid has very little coaching experience, but everyone has to start somewhere; and he is well respected by the players both as a former player and a teacher/mentor.
Recchi is an experienced assistant coach, with leadship qualities and knows what it takes as a forward to win in this league. (problem with Recchi is he may want to be head coach somewhere. Here might be an option in the off season rather than an assistant again.)
Leach becomes a fresh voice as head coach with new assistants bringing traditional seasoning.