I kind of hate more than 12 team leagues because of scheduling. If you have 2 divisions with 8 or 10 teams each, then it's like you aren't really one conference, might as well just do some kind of cross-conference preferred OOC scheduling deal, like 1 FB and a couple BBall games every year. Which might be fun for the Big12 but won't help the PAC much I suppose.
Doesn't make much sense to just take the Arizonas to get to 12. You almost have to go for the LA schools. But then you are at 14. You could toss Baylor and WV out (sorry WV, just geography) to get back to 12.
UCLA, USC, ASU, AZ, TT, TCU
Texas, OU, OkSt, ISU, KSU, KU
That would even give you the unbalanced divisions like the SEC or B1G. And OU or UT could go beat up on a big name (but likely overrated) USC or UCLA team in the CCG and get into the CFP easier.
The other 8 Pac12 teams could add Boise or Wyoming, or just stay at 8. They might do well with 8 as the GREEN conference (both in terms of environment and weed).