As a Pac-10 Alum, I would suggest that there are options to splitting the old "Pac 8" or "Pac 10" schools equitably and with maximum appeal.
18 teams (the 12 they have plus whoever)
in one half and
in the other half, with the additional 6 teams split equitably. (Utah, Colorado, etc)
That is 7 games. Add their natural rivals, who are all in the opposite conferences puts you at 8 conference games. You could add one at random if you prefer a 9 game conference schedule.
1. The California Schools would never give up playing the three of them. This was made quite clear when the PAC-10 went to 12, and California got rights to play eachother every year.
2. Zipper-split is too complicated. There was a proposal to do a zipper-split when the PAC-12 was formed, and Larry Scott rejected it in favor of the current alignment. It was a thing of beauty. The PAC-12 rejected it.
Here's the way it would have worked.
You split the teams up into divisions, one traditional rival in each division:
Washington - Washington St.
Oregon - Oregon St.
UCLA - USC
Cal - Stanford
Arizona - Arizona St.
Colorado - Utah
You further break them down into 4 geographical regions
Northwest (Washington, Washington St, Oregon, Oregon St)
California (UCLA, USC, Stanford, Cal)
Four Corners (Arizona, Arizona St., Colorado, Utah)
Each team plays all the teams in their division (5 games), all the teams in their region (2 additional games), and then 1 additional team from each of the other two divisions (2 games)
That would mean for instance, Oregon St. would have this potential schedule.
vs. Washington St.
@ Arizona St.
Larry Scott dismissed this alignment and scheduling considerations for a simple north-south split with guarentees for the California Schools. There is no indication that he would consider a zipper-split if the PAC-12 would go to 16, or above.
This is a large reason as to why there really is no reason for expansion outside of Texas. Texas provides that counter-balance to California in population and recruiting beds to provide the east division with that balance.
Really, the only alignment that will work is an east-west split, with the west being the old PAC-8. And then after that