I think it depends what camp you reside in...the one that GD actually gets to call the plays he wants therefore he's the failure or does KF dictate that more than we know and so there's handcuffs and GD will be the fall guy. If KF dictates it, then firing GD won't matter cause KF will handcuff the next guy. Everyone thought KOK was the problem...that didn't work out the greatest. The problem is it's not just one thing or one person. It's really an accumulation of things that's causing issues. It's playcalling, it's being predictable, it's KF's stubbornness, it's recruiting (or lack there of), it's stupid penalties, it's not evolving as a program, it's execution on the field....etc.
If Brian were to be promoted to OC, would that matter? Not sure. I think KF listened to Brian a little bit last yr. It at least seemed that way or the media skewed it that way. Maybe he didn't. If he doesn't, then being the OL coach on Dec 31 vs being the OC on Jan 1 will not change things one bit.
At the end of the day, KF has to want things to change and he's proven for the most part that he believes his way is the best way whether it produces or not. If he doesn't, then we are what we are until he's gone and that's a 59% winning team. Either people will like it or they won't cause he's not getting fired anytime soon.