I wanted to look at something like this, but the more P5 opponents a team has, the bigger a pain it is to go track down the P5 records of every team they faced. It means not only looking at Florida's schedule for each of the past ten years, but then also looking at the schedule of each of their opponents for each of the last 10 years. It adds up quick.

And this kind of lines up with what I'd expect. Florida is a "good" team so they win about 50% against them (44% being pretty close). I agree with all of your analysis here though, just worry we're talking past one another a bit.

You're saying "BYU would be a mid-tier P5 member, if admitted", which I agree with (think they might even be slightly above average, though not massively so)

I'm saying "BYU is currently equivalent to a lower-end (but not abysmal) P5 team".

I think both those statements are true, given that BYU would almost certainly improve (after a few rough seasons) if they went P5.