What about going to 16 as a conference that maintains its identity of the 5 western megaregions while strengthening domination of each?
Let's say, for example, that UNLV, SDSU, Boise State and UNM were added.
We'd have the following setup (Pods for scheduling purposes only):
Pac-16 North
Pod A - UO, OSU, UW, WSU
Pod B - Cal, Stan, BSU, Utah
Pac-16 South
Pod A - UCLA, USC, SDSU, UNLV
Pod B - UA, ASU, CU, UNM
To maintain rivalries focused within the demographic megaregions, each Pod plays the other 3 teams in its Pod every year. Then, the other 6 games are 2 games against each of the other 3 Pods every year.
Personally, I like this much better as a fan than expanding outside our region. I also like the representation of the entire MTZ-PTZ areas of the US as our footprint and culture. And, I much prefer 16 teams with Pod scheduling over the wonky 14-team scheduling models.
(And, as has been mentioned, it's likely that the Big 12 will expand east to strengthen presence in the Great Lakes, Piedmont Atlantic, Gulf Coast and Florida megaregions because it's much more valuable to get a piece of those than to try to get a piece of the Front Range or a major outlier like BYU. So I believe we'd end up having our areas without P5 competition.)