I think the best system would be a 16-team playoff, because you give the same type of opportunity to mid-majors that you do in basketball, that being allowing ALL conference champions in, and then having 5 at-large spots. We'll see if it ever gets there, though if the playoffs are the money-maker I think they have the chance to be, the dollar signs will likely make more playoff teams happen at some point. Whether it ever gets as big as 16, we'll have to see. Even at 16, it's less of a percentage than it is in most NCAA playoffs for other sports. Hockey only has 59 (I think that's the number, it's right around there) DI schools, but include 16 in their playoff. Basketball and baseball are around 300 schools (baseball just under and basketball a bit over) for DI, and baseball has 64 teams and basketball is at 68 teams now in their playoffs, both for approximately a 20 percent ratio of schools in playoff to total schools in the division.
Regardless, I'm just happy to see some type of playoff. Have wanted this for years. I appreciate the history, but the system has been broken for decades, and this is at least a start towards fixing that. (I never saw the BCS as a true 'fix'... way too many flaws in its setup)
For me, 16 is too many, but I would love to get to a 6-team or 8-team playoff with semifinals hosted by the higher seed, and that would be absolutely perfect IMO.
And I can see that, HS. My goal at 16 is to give all conference champions an entry. No question everyone has a chance at that point, and you can argue til the cows come home about 16, but it ends up being like 68/69 in basketball right now... really becomes irrelevant because the likelihood that team will win is reduced greatly. That's my big push to 16. Will we see it? Maybe not in the near future, but my hope is that's where it'll head. May take 20-30 years to get there...

But 6 or 8 would be great as well. I don't have a problem taking 6 conference champs and the best 2 at-large in that scenario. The question ultimately becomes how you select the participating teams, and that will be the interesting piece to all of this for me. Who do the powers-that-be ultimately trust with that duty? Personally, I'd like to allow the polls to remain, but the actual selection be done by committee. Allow some formula that weighs human polls, computers polls and SOS, and have that as ONE consideration for the committee, but not necessarily the overriding factor.