How the **** did you reach that conclusion? That's the not question being discussed. Some dummy said that co-coordinators don't work. Obviously it works pretty well for coaches with lots of national championships and dozens of other HCs across CFB. Whether co-coordinators will work for Diaz or not has nothing to do with the concept of having co-coordinators. He can have one ****ty coordinator or two equally ****ty co-coordinators and there isn't going to be a big difference in performance. If on the other hand he brings in a top tier DC and Baker is the non-play calling co-DC, it could work just fine.
As a hypothetical example, let's say Miami reached out to Charlie Strong. He's an analyst at Bama (most of their analysts make well under 100k per year there). I wouldn't be surprised if he'd happily take the title of title of play calling Co-DC to get back into the coordinating game. He'd also primarily coach LBs, so then Baker wouldn't do much except maybe fetch coffee and be the co-DC in title. The reason that Baker would be kept around is that he's under contract and Diaz thinks he could still get some use out of him (he gets paid what he's owed whether he's on the staff or not- hence the word "contract". Now what value he could possibly still have is a valid question). If the D has a big bounce back year with Strong as the playcalling co-DC, Baker's reputation gets somewhat rehabbed then some G5 team will hire Baker away next year to be a full time DC, and that team can buy out the remainder of his contract. The reality is that Baker would have to be willing to accept the demotion to non-play calling co-DC or he could resign (in which case he doesn't get paid the remainder of his contract). Either way it solves the biggest problem, which is that he's not very good at the Xs and Os and shouldn't be the play calling DC anymore.