Being top heavy is another weakness, in fact we can continue on with this list of things and they all add up to what we see happening.
The pac has a buffer zone though that the big 12 doesn't. Itll never make cultural or geographical sense for USC or Washington to jump to the SEC like it did for Texas or Oklahoma. As conferences expand though that same buffer zone could become a detriment as well vs say the SEC that could still go after Clemson, VaTech, NC State, FSU, Miami, UNC, West Virginia, Oklahoma State, etc. or the B1G that could go after Notre Dame, Kansas, Iowa State and more.