It actually increases the importance of the conference championships. The current system already makes allowances for the importance of conference championships but this year there is a good possibility that only 2 of the 5 conference get represented.
Hey, a 9-4 NW getting in (not sure where you get 8-5) doesn't bother me in the least over the teams you mentioned. I doubt those teams would be quite as successful as their current records if they played a Power 5 conference schedule so I don't hold those teams in as high regard as you do. Even a down BIG10 in 2018 is legions beyond the conferences those teams play in. btw, I only suggested the top 12 (maybe 15) rating as an idea. I suspect it would rarely come into play but as least it is a safeguard. For example, this year it is highly doubtful that either Pitt or NW is going to be within 20 points of the Clemson or OSU.
Funny thing is, a team like UCF has a better chance of getting in with an 8 team playoff with auto ins because no conference can have a beef if theoretically their "best" team is in. And teams like UCF(whose 12-0 is a testament to their weakness of their schedule, not their quality) might actually get to play some better OOC teams if the Power5 teams aren't afraid of that one quality OOC loss (i.e. like Michigan if they hadn't swallowed their dick).