I have to think that
I have to think that if this is the case, that they will heavily go after the AAU schools from the Pac-12. It all starts with USC. They know that the Pac-12 will always be a "2nd tier" conference compared to the Big Ten and the SEC. Their brand has taken a bit of a National Hit over the last decade or so. If you get USC on board, then I think it's an easy sell to get UCLA, Oregon, Colorado, Stanford, Cal. Taking those 6 Schools gets you to 20. Ideally, I think you'd like to get to 24. If that means adding Kansas, Washington, Arizona, and leaving a spot open for ND, then I think you go that route.
I know that ND has their GOR stuff, but if you put pressure on them by saying that unless they join, none of your league schools will schedule them, that takes away their marquee games against USC, Stanford, and Michigan, which would be a financial hit for them eventually.