Even though Kansas and Missouri wouldn't have made it into this proposed playoff, the argument against their inclusion is strong: they didn't win their conference! West Virginia would have made the cut.On-the-field performance is the only real metric we have for to measure sports teams. Allowing only conference champions to participate in a playoff would enthrone on-the-field performance as the ultimate arbiter between post-season haves and have-nots. Do you want a berth in CFB's playoff? Win your conference.
In a world with this kind of playoff (which is, admittedly, a fantasy of the highest order) the BCS/non-BCS distinction would lose most of its meaning, because in most years two of the five non-BCS conferences would suddenly have a guaranteed place at the table. This would re-incentivise geographically-defined conferences, because all conferences would be created (nearly) equal in the post-season.
Is your conference too hard? I think of Texas Tech, Connecticut, Oregon State, Missouri, Ole Miss, Georgia, Clemson... These are just some of many teams from privileged conferences that sniff occasionally at a title crown, but never seem to get themselves together enough to snatch it away from the entrenched elites in their respective conferences. What hope for them in a champions-only playoff?
There's an easy answer; so easy it's reducible to one word. Move.
The SunBelt would faint with joy to include Mississippi State and Clemson; Oregon State to the WAC? Texas Tech to the Mountain West (not necessarily a downward move for the Red Raiders...)? Why not? An evening-out of the D-1A conferences would be the best thing that could possibly happen to college football, and allowing only conference champions into an eight-team playoff would be the best way to prompt that change.
Besides: if winning the conference is the ticket to the playoff, there's no devaulation of the regular season to worry about. Conference championship games would be even more important, and best of all, the BCS crystal trophy would actually mean that awful line that's said about it when given: from the eleven BCS conferences...