2006-2009 was awesome - nationally ranked, conference titles, beating Utah, etc
Realistically what on earth do BYU fans expect more than 2006-2009? The PAC 12 or Big 12 aren't calling. And complete irrelevance starting each October completely sucks.
BYU has no chance of doing anything better than 2006-2009 (#25, #16, #14, #12) as an independent. The ceiling is at best an NY6 game and that is somewhat of a pipe dream already given the current structure (see last years quirky season).
BYU has a better chance of playing for a national championship as a member of the AAC than they do as independent.