They would easily beat the Ragin Cajuns in a rematch.
If I understand correctly, the logic is:
ISU would beat Louisiana in a rematch, thus ignore the early loss. However, pay attention to ISU's wins, as without a doubt they have no chance of losing those games in rematch.
While I respect that teams do improve/decline during the season, all we go can by is when they played. When they played Louisiana, they lost. Not only that, they lost twice. Would they hammer the other team that beat them this season if they had a rematch?
ISU lost _two_ games. In a season with less than the standard 12. To me that is a fatal flaw as far as making the playoff.
If instead, you want to make the playoff be 8 teams, with each P5 champion guaranteed a slot, then if they win the Big XII title game, they are in. But putting them in the top 4 in a very chaotic beauty contest? No, I don't think they deserve that. If they only had one loss, I think the argument would be stronger, but still, losing to a Sun Belt team?