This post really tells the tale. There is a tendency here to frame the issue as "Mac Lovers" vs. "Mac haters": a childish oversimplification in part the fruit of unwillingness to face that this team is deficient in nearly every area. Mac is probably not a good enough player that we should commit to him long term, but It is difficult to say with certainty whether this is so because of Mac's insurmountable limitations or because of the HC/GM's fireable incompetence in failing to build a decent team around him, and in failing to let go of his asinine and petty resentments, and of his compulsions - going back years - to deprive the team of players' services - even at the expense of losing a Super Bowl - to assuage his petty, butt-hurt resentments.
Given all this, I would:
1) Keep Mac another year as a sort of placeholder starter until whatever OB candidate we draft or trade for is able to beat him out.
2) Fire Bill the GM, relieving him of any role whatever - beyond such advice as in welcome from any HC, advice which the GM may value as he chooses.
3) The Krafts should convey privately to Bill that though he is welcome to stay another year as HC, it will be on a probationary basis, given his failings as HC.
4) I understand Bill is unlikely to accept such a role. I don't care. Though he is not the blatant failure as HC which he is as GM, the trends are not good: the game plans blow, the in-game adjustments are hit or miss, the team has lousy fundamentals, decisions as to which players are active on game day are inexplicable to the point of being toxic for team chemistry, and so on. If Bill will not accept being fired as GM and serving on a probationary basis as HC, I'm fine with that. Just look at this team. It's a mess, right?
(This has indeed "already been discussed," and it will be again. Dealing with a failed GM and a failing HC must be Job (and topic) One, particularly given that decisions re this team in years going forward are in the immediate offing, and we do not want a failed GM to play a central role in important roster/trade/draft decisions soon to be made.)