BYU’s defense would have continued to do the same on all subsequent possessions, without any adjustments made by SMU to help Stone. I mean, come on, this is BYU’s D we are talking about. They matched up well with SMU. I think with some adjustments by SMU to help Stone, they could have possibly/probably ended up with about 10 more points than they did.
If it as you seem to believe, that SMU would have easily failed miserably with Stone out there longer, then SMU may have trouble making a bowl game. I think you are overestimating what BYU’s D would have accomplished if Stone came back out with some additional adjustments by SMU.