This is slightly incorrect since I missed one P5 win in there somewhere, but does a pretty good job answering the question. And I was mistaken, it has made a big difference.
Vs "Strong" P5 (those who finished >.500 against other P5), BYU was 5/23 (21%)
Vs "Weak" P5 (those who finished <=.500 against other P5), BYU was 11/19 (58%)
Which again supports the argument that we'd basically be in the same range as the weaker P5 teams. And with expected improvement from being in a P5, we'd be middle-of-the road, not great, but nothing to be embarrassed about either.
It was when I broke down the home/away for each grouping that the location ended up not making a huge deal.
This post was more to look at the ramifications of being Independent vs G5 though, which is why I went back to our performance in the MWC, and unfortunately don't have the data breakdown for that one.