It is easy to see who the three protected rivals of Wisc., Nebr., Iowa, and Minnesota would be. Maybe Wisconsin would not be a protected rival of Nebraska, and instead have one or both west coast teams as protected rivals along with Iowa. It becomes more difficult to identify three protected rivals for most of the rest of the Big Ten, including USC and UCLA.
I am not sure USC and UCLA will want to more regularly cross three time zones to play teams in the Eastern time zone, or that Eastern teams will want to cross three time zones regularly to play night games on the west coast.
It will be interesting to see how they work this out.
Historically, the only Big Ten school USC does not have a winning record against is Penn State -- against whom USC is 3-3. The west might start winning divisional championships with USC joining the BTW.