The big thing with adding lacrosse is the cost, and all the western schools are in the $1 million a year and more to play D1 Lacrosse. It would help if UND had a lacrosse club team (I couldn't find UND on the MCLA website).
If UND added lacrosse, a western conference could be created and other schools would need to buy in also that have club level teams. Denver and Air Force most likely would like less travel and get Colorado College to move up to Division 1. Then you have 7 schools in the Big Sky and 4 NCHC schools have club lacrosse teams and toss in NDSU, SDSU, and USD's club teams and that would be a nice size conference. Frist it's going to take money and getting other area schools to add lacrosse as a varsity sport on both men's and women's for it to work.
Colorado State adding women's lacrosse and joining the 5 Pac-12 teams would give the Pac-12 an auto-bid.