I find it very difficult to say that Carr is broken when I see other great players all over the field under performing. Having seen it since last season, Carr is just the latest player not playing well in this system if you can even call it a system. I think he's being scapegoated because he's the new guy that was supposed to fix things and it all just looks the same.
So for me it comes down to who can they bring in to get the best out of all of our players on offense. Do they run a blocking scheme that works with our guys on the o-line? Do they have a screen game that can make use of AK in space? Do they have plays that can make use of MT, Olave and Shaheed with all of them playing to their strengths?
I don't know enough about coaches to know the answer but, while I appreciate the question, I think the real question is far broader than the one you're asking.