As long as CFB has 130 D1 teams and 10 conferences...an objective system is impossible. I don't want them to blow up the system to allow access to Fresno State and UL-Lafayette. They shouldn't be in the same "league" as Alabama and USC to begin with. But as long as they are "equals," you need to use subjectivity (and common sense) to realize that Alabama is better than UL-Lafayette, even if they don't square off on the field.

That said, my proposal combines objectivity and subjectivity nicely.
Five auto-bids. Conferences would love the money available for their CCGs because
Two at-large. Let the debate rage between idle non-CCG participants (like OSU '16 and 'Bama '17) and strong CCG losers (like Iowa '15 or Michigan '06).
One G5 rep. Again...mostly subjective in choosing which team gets a chance, but at least UCF doesn't have to end their season in frustration.

Seed them...1-8...with top seeds hosting two weekends after the CCG weekend. Home field advantage is a huge advantage and teams will still whine about being #5 instead of #4 and getting the home field advantage. The seeds mean VERY little currently (as the top 4 teams on a neutral field are EXTREMELY equal)...but #7 is more likely to play a much tougher team than #6 will...so the seeding matters.

Semifinals then use the bowls for neutral sites.