i agree with the sentiment that ranking coaches is a near impossible problem. however, i think it would be cool to keep some lists, like, top 25 longest NT streaks ever. maybe one per round of the tourney. and/or maybe some complete lists, like, a complete list of every coach to win back to back titles, or to make 20 straight NTs, or something like that.
i think a few people already have a program to scrape the history page off of every team in a division. a couple of the studies people have posted suggest this is true, as well as the dynasty lists. one nice thing about lists like the one above is, they are not subjective, and they can be generated by a program if the history page data was available for all schools. even if that data is not available, im sure getting it is a much easier problem than coming up with anything manually!