Not even a G5 champ. There is no guarantee that BYU would ever win the AAC championship, or that it would be the highest ranked G5 champ if they did. BYU could win the AAC championship and still be passed over by the playoff committee for the MWC, or CUSA champs.
All we would be doing by joining the AAC is trading a number of high quality games against name brand schools each year for games with deplorables like Memphis, Houston, and East Carolina. 🤮
No thanks. Joining a G5 league for imagined access to an expanded playoff would be folly.