Tucker has never been a successful coach at any stop. He's not a guy who's going to outscheme you (100% certainty).
I think people are looking at this the wrong way. The defense is in shambles, it's one of the worst in the league. It's not a 4-3, 3-4, 5-2, it's all wrong. You can hire any coach you want right now at this very offseason and build a new defense that fits this guy.
So the real question is, is Mel Tucker better than all of the other coaches out there? There is no continuity right now. There's no 2nd year in Tucker's scheme because it just won't be that kind of improvement. So is Mel Tucker better than Ray Horton or Wade Phillips or anyone else out there the casual fan doesn't know about? Are you more excited with Tucker back there than the 2 mentioned above or maybe a protege from one of the best defenses in the league? I just don't think in your heart you can say Tucker is better.
So why are we going to waste another season? He's going to fail next year, and the Bears are going to be back to where they are right now. Likely 8-8, 9-7, not good enough to overtake the Packers. Then what? You fire him after you spent an offseason drafting and signing for him and the entire team is older, and you're now wondering whether Trestman and Emery are already on the hot seat.
It just does not sound favorable. Forget Lovie Smith's defense. Fire Tucker, sign a guy who will be a long-stay guy on this team for the next 3-4 years, and see if the Bears can attain success with Trestman without a question mark DC (aka sign a guy you know can coach successfully). If then it doesn't work out, you know that Trestman cannot lead this team for sure. Not like Lovie where you keep thinking the OC was the problem.
Tucker is the guy you pick when no one else will come. He's the guy who's willing to coach for you when your head coach is on the hot seat and might be fired next year, such as Tice, Bates, Martz- coaches who were the worst case scenario basically.