Frost is the CEO of this staff and it's ultimately up to him to decide which assistants give the team the best chance to win. Thus far he has not shown a great willingness to part ways with his staff, and the exit of Walters appears to have been mutual. If Frost truly feels he has several more years as HC regardless if the team continues to underperform, he will be inclined to keep most if not all of the current staff. However, if he is feeling some pressure from Moos, Green or Carter to show substantial improvement in year 4, he may be willing to rock the boat and make some broader changes.
I agree with many of the posters that we have seen some marginal improvements on defense over the past 3 years, while the offense and special teams have really struggled. With that said, I am not sure we should be seeking even just marginal improvements when the baseline we are improving from is so low. Instead, we need to be swinging for the fences with assistants and finding coordinators that can help give NU the best offense, defense, and special teams in the BIG West division. To be truly competitive on the national stage you really need top guys in all 3 phases of the game.