Arizona, Arizona St, Colorado, Utah, BYU, Boise St, and either UNLV or Colorado State
I added 7 because it's sounding more and more likely that WVU will be moving to the ACC. If WVU moves to the ACC, it makes a lot of sense for the B8 to go boldly West.
That would be a strong 14-team conference with an East and West division:
East: Texas Tech, Baylor, TCU, Kansas, Kansas St, Oklahoma St, Iowa St. UNLV or CSU
That makes two divisions that both make geographic sense, and would both be pretty balanced.