it turns out good for bad for BYU depends on a couple factors:

1. If the Big 12 falls apart (e.g. the remaining "top" teams end up in the Big 10, SEC, PAC-12), then I could potentially see the American conference swallow up the remaining few teams to get themselves to 14 and essentially make that no longer an option for BYU to join. This would be a "bad" option for BYU simply because it would put them in a spot where the status quo is still independence BUT would remove 2 of the potential landing spots in case BYU were to ever pursue joining a conference.

2. If the Big 12 remains intact, they will likely do so by expanding back to 10 or 12. Whether this ends up good or bad for BYU likely depends on whether or not they are one of the teams included in that expansion.