Paul Johnson should be on the short list.
My list in order of who I think would be right for the job:
Paul Johnson-Has won games at a good school, but I think he can even do more at a bigger named school.
Gary Patterson- this would be a homerun hire, but he would need the right OC. Frost as coach in waiting type thing is what I am thinking with Muschamp at DC.
Jim Tressel-Maybe the best common sense hire. If not for Urban Meyer sitting there in waiting, would still be coaching at the Buckeyes, we all know that.
Bronco Mendanhall- Solid program with good ethics.
Mark Richt ( this one I have doubts on, but he can recruit legit talent)
Jim Harbaugh- Why not at least think about it and interview.
Scott Frost- I would like to see him at least come back as an OC first. Maybe down the road could be head coaching material. Has learned from some of the best however- Osborne, Chip Kelly, Parcells (JETS), Walsh (Stanford), and one season under Snyder at KSU. Pretty good list of mentors.