the fact that (a) the biggest problem from P5 conferences RE CFP is that there are 4 CFP slots and 5 power conferences. this quickly resolves that issue and helps bolster what is uniformly considered the weakest one (ACC). "but the 'big 12' would still be a P5" you say...well sure in name, but they will quickly become 2nd-class, not unlike the BigEast of the BCS era. the Big12 champ will have to win some pretty convincing OOC games and look stellar to get into the CFP. the "power 4" champs would be given default status over anyone else.
and (b) it helps group and consolidate the best G5's (and BYU) into one conference. people talk about the CFP expanding, i think the first big change will be removing the G5 auto-bid. if what blubrotha says is true this would help justify that change. maybe a G5 bid is still available to any high enough ranked team but there will be no auto-bid b/c now the best G5's are given access to the Big12's NY6 bowl slots.
some more evidence that helps bolster the claim...the Big12 and ACC have been the most outspoken about removing the restrictions on how the slot 2 teams into their CCG...most assumed it was for a different reason, but this is evidence that this particular move could be possible. in addition P5 conferences have pretty much dubbed BYU a P5 by name and some have recently added Cinci and Uconn to that mix as well...future additions to Big12?
this scenario seems incredibly complex and would require the joint assistance of many moving parts to pull off which is why it seems outlandish to me but i'd be happy with those results. and it wouldn't require an expansion to CFP which i believe many with power are very against.