Baylor

Positives:  Good academics, current P5 affiliation, very good basketball
Negatives:  Poor football, both historically and recently (only good seasons were with Briles and ended in disgrace from scandal and a brief resurgence with Rhule who then immediately left), religious affiliation (negative from P12 standpoint), private school, poor TV viewership, major scandals, weak market/fanbase, not a Tier 1 Research Institute

TCU

Positives:  Very good football team (3 top 10 finishes this decade), current P5 affiliation, large market, solid TV viewership, excellent baseball
Negatives:  Religious affiliation, fanbase doesn't match market, private school, not a Tier 1 Research Institute

BYU

Positives:  Best football history of available options, geographically convenient (Utah/BYU, Colorado/Kansas St, Texas Tech/OK St become the new rivalries), good academics, good basketball, good facilities
Negatives:  Weakest TV viewership, weakest football over the last decade, current lack of P5 affiliation, religious affiliation (even more than than TCU/Baylor because it takes a more active/engaged role here), SLC market already in PAC12 (not a huge thing, but harming an existing program should ideally be avoided if all else is equal), Sunday play (not a huge thing, but a nuisance), private school, not a Tier 1 Research Institute

UNLV

Positives:  Great facilities, new large-city market, similar mindset to PAC12 schools, most geographically convenient (Utah/UNLV, Colorado/Kansas St, Texas Tech/OK St become the new rivalries) especially with PAC12 HQ moving to Vegas, Tier 1 Research
Negatives:  Poor athletic success, poor academics

UNLV is a tempting choice since they have everything the PAC12 would want - flagship state university in the area with large population and similar mindset...it's just unfortunate that they're so bad at sports.  The potential is there.  That's the selling point got both UNLV and BYU.  Right now BYU is blown away in TV viewership by TCU (for example) and fields substantially worse football teams.  But with BYU or UNLV, you're making a bet that they'll improve if they go P5.