It's probably hard to find protected rivals for USC and UCLA. New additions to the conference (UCLA, USC, Rutgers, Maryland, Nebraska) don't really have long established rivals
If I had to pick 3 rivals for IU, it would probably be PU, Michigan St and Illinois. Although the question would be if we would make those teams top 3 in rivals.
Personally, I would just do pods and only have 1 protected rival
Indiana - Purdue
Illinois - Northwestern
Michigan - Ohio State
Edit
Wisconsin - Minnesota
Iowa - Nebraska
Rutgers - Maryland
Penn State - Michigan State
UCLA - USC
I don't know what other schools necessarily think is their biggest rival so a few of those may be off.
If I had to do 2 rivals
Illinois - Indiana, Northwestern
Indiana - Purdue, Illinois
Iowa - Wisconsin, Minnesota
Maryland - Rutgers, Northwestern
Michigan - Michigan St, Ohio State
Michigan St - Michigan, Purdue
Minnesota - Iowa, Wisconsin
Northwestern - Illinois, Maryland
Ohio St - Michigan, Penn State
Penn State - Ohio State, Rutgers
Purdue - Indiana, Michigan St
Rutgers - Maryland, Penn State
Nebraska - USC, UCLA
UCLA - USC, Nebraska
USC - UCLA, Nebraska
Wisconsin - Minnesota, Iowa
PODS
1) East Division: Maryland, Rutgers, Penn State, Ohio State
2) Not so East Division: Michigan, Michigan St, Purdue, Indiana
3) Not so West Divison: Illinois, Northwestern, Iowa, Wisconsin
4) West Division: Minnesota, Nebraska, UCLA, USC
I think the above separates it well enough and puts schools together that are located close together (outside of pod 4 but no pod with the CA teams is going to be close to each other).