The ACC has, and continues to have, a tie-in with the Orange Bowl itself. That auto-bid belongs to the ACC exclusively. The MWC has no such auto-bid itself. It just has the "best of G5" bid. So, in my best guess, the MWC, or any single G5 conference, doesn't have the right to allow an agreement to a team like BYU, at least not without the support of the other 4 G5's. Does that make sense? So theoretically, I believe it would be just as easy/hard for BYU to reach an agreement with the enitre G5 for inclusion in that process without having a scheduling agreement with just one G5 conference. And that's if the G5 themselves have the right to make the agreement, which I'm not sure of.
Regardless, I just don't see it happening.
That is just my best guess on the situation