Schools more likely to get in the pac-whatever than Boise.
Texas (a team the Pac would want more, but not be able to get due to 13-year tv rights agreement)
Ok (see Texas)
Ok St (see Oklahoma & Texas)
Texas Tech (see OSU, Oklahoma & Texas)
Kansas (they didn't pursue them before, but see Texas Tech, et al)
Kansas St (they didn't pursue them before, but see Kansas, Texas Tech, et al)
Hawaii (I once thought UH might be a target, but not so much any more)
UC Davis (Pac won't invite someone who does not have a major college FB program)
University of British Columbia (Pac will not invite someone who does not have a major colleg FB program)
Baylor (they didn't go after them before, but see KSU, Kansas, etc.)
Iowa St. (highly unlikely, and also see Baylor, KSU, etc.)
UNLV (this is a possibility, even though FB is not up to snuff)
Nevada (somewhat of a possibility, but less likely than UNLV)
Sdsu (Pac is unlikely to go after any more California schools)
New Mexico (doesn't seem too likely)
Air Force (a good possibility, but Air Force might not go for it)
Colorado State (somewhat of a possibility as a fallback if they can't get Air Force)
BYU (a good possibility if they feel the need to expand)
Montana (not sure they would take an FCS move up, but this would be the team if they did. Don't know if the Griz would be willing, though)
Idaho (slim chance, if any)
USU (very slim chance)
NMSU (very slim chance)
So, from your list of 22 teams, the 8 Big 12 schools can be eliminated right off the top, as can British Columbia, UC-Davis & San Diego St. You can also toss out Idaho because they wouldn't be considered ahead of Boise St. That knocks you down to 10 schools. Here's my evaluations of the teams that are left:
Likely top choices: Air Force and BYU as companion schools to Colorado and Utah. Air Force is on pretty equal footing with the bottom 8 of the Pac-12 FB programs, and has stepped up somewhat in basketball recently. BYU has a better-rounded program than Colorado or Utah, but might be a difficult fit due to religious concerns and dealing with their own tv network.
The second tier is more crowded, but would likely include Boise St., Colorado St., UNLV and Hawaii. Boise has the better FB pedigree by far, but would have to expand their stadium and add baseball - which shouldn't be a problem since they would be getting more money for tv rights. I'm not sure what their academics are like, but Colorado St. might be the fallback school if they can't land Air Force. UNLV might help in basketball, but the league might not want to expand into Sin City. Hawaii would be an expensive add, but has a pretty well-rounded athletics program.
That leaves you with Montana, Nevada, Utah St., New Mexico & New Mexico State. I think Montana is the strongest of these players, and with the upkick in tv money the Grizzlies could easily expand their stadium and keep it filled with rabid fans. Utah St. might be a distant fall-back option if the league was unable to land BYU, and Nevada would rank even lower on the totem poll since Reno is viewed as "Sin City-Light". I don't think the Pac would be interested in moving into the state of New Mexico.
So, from my point of view, Boise St. would rank anywhere from 3rd to 6th on the Pac-12's expansion calendar, unless they are willing to wait for the Big-12's tv rights deal to expire. And the Pac is unlikely to expand unless the Big 10 decides to do so, as well
