Brewing, what you say is spot on IMHO, but it all starts with our Head Coach and he, after 20 years, IS NOT CHANGING, but without a doubt, the best college defensive coach in the game, not even close.
GMFP is many things, good and bad depending on one's perspective. He does indeed change, though. Remember, after the horrid 2013 season he brought in guys to completely change what our offense did. Where he is stubborn is in the loyalty department, and 2013 is again illustrative in that the guys who were bitter failures in various positions were kept on staff, but moved to new positions. Heads did not roll as they would at any other program. GMFP's career before TCU was like many: nomadic and poorly treated. I believe he made a vow to himself to be different, to not treat assistants like chattel but to treat them like valued partners. Comrades. Good, or bad, dependent on perspective.
It is obvious that to be a good, even great defensive mind, you must understand offenses. You have to know how they work before you can stop them. GMFP also has a sneaky sense of their mindsets, seemingly knowing what they are going to do before even they do. From his standpoint, he felt that he would go with the type of offense that gave him the most trouble: Air Raid. He got good disciples of Mike Leach to implement it. He surrendered playcalling and all things offense to them. That indicates that the Old Dog is indeed willing to try new tricks, even ones he hates at times. He surveyed the overall scheme and determined that he needed a new strategy, and implemented it. Then, he stuck to it. 2014 to now has produced three 11 win seasons (or better) based on this new offensive scheme. 3 out of 5 seasons were pretty darned good ones, considering.
The bad seasons, though. Ugh. How can such swings in fortune happen? This off-season, like the Spring 2017 period, will consist of plenty of sit downs to determine 1.) What Worked, and 2.) What Didn't, and 3.) Why. I am sure that behind closed doors these meetings can get pretty heated, and that much truth is laid bare. TCU has seemingly done well after such painful but necessary adjustments. 2013 begat 2014, as 2016 begat 2017. There is no doubt subtle changes will be made, but a question that flummoxes me is, with the continuity in coaching, why the swings in performance? Why the differences year to year in fundamentals, organization, poise, etc? One would think that such sameness in coaching personnel would result in sameness in performance. But, alas...
One thing is certain: In GMFP I trust. I may not like some decisions he makes, but I have no way of knowing the facts behind his reasoning. His judgement has proven sound in the long run, though. Time and time again.