In order from highest choice to least
Hue Jackson- I believe he never got a fair shot in Oakland. In 2010, as offensive coordinator, Jackson's offense put up some killer numbers, and McFadden had his best year as a pro. The next year Jackson was chosen to replace Tom Cable as HC. the Raiders went 8-8 (3-3 division wise) after a 7-4 start in Jackson's lone HC season. Jackson known as a tough minded run-first coordinator, though he's complimented as a good QB molder.
Chip Kelly - If you haven't heard of Chip Kelly yet then you should probably leave your house, or come out from under the rock you're living. Kelly is the man who made Oregon football relevant. He's an offensive genius (and not the Martz kind). Kelly's Oregon teams have been offensive juggernauts since him taking the helm. With a bowl appearance evey year, including a BCS championship appearance, Kelly certainly has the resume' to interview for NFL HC.
Mike Zimmer - The defensive coordinator for the Bengals. I know what you're thinking "not another defensive meatball guy", but bear with me here (hehe see what I did there). Zimmer's defenses in Cincinnati have been very solid. In my opinion he is responsible for Marvin Lewis still having a job.
Sean Payton - Well, ex-Bear. SB winning head coach, may not be allowed to coach in New Orleans. If he can't get back on in NO, I believe the Bears have to interview him. He runs a great program (no matter what his idiot DC does), he's a class act. Payton could be a very good hire for the Bears.
Perry Fewell - Lovie 2.0. Fewell is a tampa 2 disciple, though his version is more active and blitzy than the Lovie Smith version. Fewell, as you may recall, had an interview with the Bears for DC, but took the Giants job because he though Coughlin was on the hot seat and it would give him an inside track at the HC job..One Sb ring later... Fewell would be a great choice at HC, because it would give the bears a young face, and change of culture, without having to change the scheme completely.
So there you have it. Those are my choices for who I believe should get the job interviews for the HC job if (god forbid) Lovie gets fired.