I'm not sure that Kelly's response implied that he would expect (or want) to play BYU every time for the 13th game. I'm assuming the 13th game would only be for Independents, (BYU, ARMY, or UMASS) but he also could have just been suggesting it in the sense that ND would be allowed 1 extra game each year, like the Hawaii exception, where ND could schedule that 13th game against anyone. But I don't see how that would really follow the whole point of this concept.