If ISU and OSU win out, ISU will deservedly surge way ahead of OSU in the CFP rankings. We beat them earlier and we will have played a tougher B12 schedule than them. I half wonder if Gundy would let ISU take its place in the B12 championship anyway.
This idea that it will come down to who had the best record against a common opponent is foolish. As this article points out, there is a chance that 8 teams could finish in a first place tie at 6-3. What if there is no common opponent among the teams in the tie? Are the ADs going to have another meeting... only this time after the season has ended?
The tiebreaker rules need to be rewritten, and they need to be rewritten NOW. Don't wait until the season is over.