People can call me crazy and I don’t care, but if it were me I’d add Stanford, Cal, San Diego St, UNLV and SMU tomorrow as a 5 team Western Division.
Develop those programs / markets over the next 5 years and use it as a springboard to target the best Big 12 programs.
I don't think you're crazy, and I do think there's some merit to trying to develop those markets and programs with the better access to the playoff and more money flowing through them (given that they'd know how critical the opportunity was).
That said, my cut off would be SMU. I would study SDSU and UNLV more before offering them. They're still going to be there in three, five, seven, 10 years. They're not getting into the bigger leagues and they're not a sure thing to develop their programs to the level needed, they're far from a certainty.
To me planting a flag out west is important, keeping Stanford alive and well as a program is important to the western strategy, and SMU has a ton of potential and letting them start now has a lot of value. In five years I'm not sure SDSU and UNLV will be the right choice, and we don't have to make it today, so we might as well not.
The fact that Stanford, SMU, and possibly Cal are willing to pay their own way for a while also makes a huge difference here IMO and I can only assume that's not an option for UNLV and SDSU. Being creative with that money could be the difference in eventually losing four to 10 schools from the current conference or perhaps managing to stop the bleeding at two more. Perhaps finding a way to juice the payouts for the most successful programs, including hoops to a higher degree than anyone else will, can ultimately give UNC and UVA something to reconsider.
I do think UNC and UVA would settle for slightly less money to stay in the ACC because of the history, cultural fit, and power they have within the conference (UNC in particular). Like if it's $100M a year vs. $60M a year, sayonara. But if it's $100M a year vs. $90M a year, maybe they stay. Where the line is, I don't know, but I would guess around 85%.