Coach 2709,
One thing the playoff system has not changed: every team that is not an undefeated champion of a power five conference is engaged in a beauty contest whose subjective rulings will never satisfy the fans of the excluded teams.
Once you lose a single game, you are at the mercy of the opinions of others. If you don't like it, run the table.
The scenario you describe would not shed meaningful light on what decision the committee should have made. What a fired up, chip-on-the-shoulder Big 12 co-champ does in a bowl game against a Big 10 or SEC team that didn't make its conference championship game will not say anything about what would have happened in a TCU/Baylor vs. Alabama match up--but that won't prevent partisans from trying.
It could be worse. Imagine if we still had the BCS structure and someone had to justify leaving Florida State, Oregon, or Alabama out.