The problem with that though, is that you devalue conference champions when you simply allow teams to get in based off of ranking (rankings shouldn't be a thing, especially not from human minds). Sure the SEC has had 4* teams in the top 10 this season, but those are just rankings and its clear Kentucky and Florida, and possibly even LSU aren't nearly as good as their ranking suggests. If you're a good enough team you will win the games that matter and win your conference and therefore be rewarded with a playoff spot. Rankings are very subjective and in my opinion, biased (especially when decided on by people not computers), and shouldn't be the determining factor of how good a team is. Winning your conference does a much better job at deciding that just about every season.
Adding to the 8 team playoff, I think the NCAA should incorporate a rule that makes every P5 team play other P5 teams in the non conference and eliminate the G5. So there would be 3 wildcards and not a G5 champ. Putting the pressure on teams like UCF, Boise, Houston, BYU, ND, and so on to join a major conference and gain they respect they deserve. As well, all conferences should play an equal amount of conference games. Currently the BIG and SEC are rewarded with cupcake weeks because they only play 8 conference games.