Nine plus KU!
More works better than less, as it allows most of the Pac 12 games to be on the west coast, and most of the BIG teams to play in the BIG. Maybe 8. 6 premium brands plus CU, Utah (and KU) as a bridge. Maybe 9, with those plus ASU or Zona (or both minus Utah). Don't worry, I think scheduling would be pod based, so Iowa moving to the PAC half is rough, but not prohibitive (CU, KU, NU, Utah, AZ, IA). If Iowa doesn't like it, i know a school in Iowa that would kill to beat up on NU.
Think of it as the Alliance, but with revenue sharing.
I don’t think 6 is enough to keep the Pac12-BIG rosemance alive, but that is probably the profit maximizing number and that’s better for Iowa St.