I have thought of a way to increase the amount of job turnover at Division I and am interested in getting some feedback on it.  

My idea is to add the ability for a coach to challenge the job of an existing coach (probably anonymously).  In order to do this, the existing coach would need to have been at the school for a given number of seasons (say five) so that they have an established track record at the school.  The challenging coach would need to have a given number of prepaid seasons (say three) on their account to ensure that they will stay at the school (and possibly also require the coach stay at the school for a determined number of seasons).  I would also consider giving the challenged coach an advantage so that if the coaches were relatively even, the challenge would fail.  I would also always give a human the job over a SIM.

This would ensure that the high level programs have a competitive squad and anyone that took over one of those programs would be on notice that if they do not perform, they are going to get replaced.

Any thoughts?

I don't think you fully fleshed out the idea here (what constitutes a successful challenge? what happens next?) but nonetheless I don't think this would help job turnover the way it needs help. The jobs that lack turnover (if any?) are the ones with high-A prestige. The C jobs are difficult enough as it is.