Yes, UNLV's basketball team would raise the competition in the WCC.
But where would their football team go? Very seriously doubt the MWC would let them be a football-only member.
Remember, in all of this conference realignment stuff, football is the straw that stirs the drink. It's the only thing that matters. The WCC is a convenient home for a team that is either independent in football or is invited as a football-only member to a BCS conference. And it played that rule beautifully when it snagged BYU. And it could play it again with Air Force.
Remember, when it looked like the Big 12 might totally blow up, Kansas was unwanted by everyone because they suck at football. A Final Four/Top Ten-type team every year in basketball? No one cared.
There's no way UNLV would ever, ever, ever jeopordize its football program to join the WCC for basketball.