I think the CFP will never happen for BYU or probably 120 of the 130 FBS schools. It would take two or maybe three consecutive seasons with probably no more than 2 or 3 losses total to get in. I’d spend $1,000 on lottery tickets before I’d put $20 on that bet.
At least until it expands to 8, hopefully in the next few years. Then there would be a semi-realistic chance with an undefeated or possibly 1-loss season.
I don’t believe the odds change much for the CFP regardless of independence or G5 conference.
However it would be potentially easier to get 11 wins playing a G5 schedule, based on a more even schedule (not completely front-loaded) and even more sucky opponents.