Here's the reality. In both RL and in HD, a coach who is doing really well at a mid-major is not going to win a title until he makes the jump to a Big 6 team (yes, exceptions are possible). But that's the deal. Earn your way to the Big 6 and then compete for a title.
Now, that means there have to be Big 6 slots to move into. I'm not aware of a single year where there were no Big 6 spots open, but it is also true, that there aren't that many. Firing logic has to be improved, both to give bottom feeders a longer time if they are building a good team and to hold a top team accountable and not let them out of the doghouse solely because they have one good season.
Finally, if you are going to increase firing, you have to make it easier for a bad Big 6 coach to have a shot back -- make them more competitive for mid-level DIs if they are fired from a top job (see Lavin, Steve) and a coach that flails out at Purdue or Wazzu needs a shot at a good mid-major.