Any of the UC schools would be a boost to the WCC's academic reputation, though as I just posted in a resopnse to Dons69... academic reputation is more about a "level" playing field in terms of admissions requirements for student-athletes than bragging rights about being smarter other conferences.
Relating to expansion, just to keep things in perspective:
Missouri Valley Conference
To me, it's doubtful that the A-10 would be interested in poaching any of the WCC's teams simply because of the distance factor, though I can certainly understand the temptation. Gonzaga, BYU, and SMC would all be a nice piece to any competitive mid-major conference. Still, the A-10 is primiarly a mid-Atlantic conference with a handful of midwest teams rather than the other way around.
If the MVC were desperate and needed to add members, I could see them sniffing around teams like Denver, or even Gonzaga or BYU. Still, the MVC is primarily a bus leage, similar to the Big West. The longest distance between any of its schools is 600 miles. That's less than the distance between Portland and any of the Bay Area schools; the distance between Goznaga and USD is more than 1,300 miles.