Odds vary with the event is being assessed. The odds are about whether riding the plank at SC is a good route to the NFL. To calculate them based on past data, you need to know the total number of pine riders at USC. A naive estimation would use that number as the denominator, and it is much larger than 1 (the numerator) represented by Matt Cassel.
Cassel was picked, in part, because Norm Chow talked about signing him after the draft as a free agent. His being drafted was a big surprise to most who follow the NFL draft. So, part of improving JS's odds of replicating the Cassel route is to have Bates take an OC job in the NFL.
Also, Cassell was picked in a draft that selected 14 QB's--and he was the 13th of 14 with Harvard's starting QB being the only one selected after him. So, using just this draft alone, playing QB at Harvard would yield similar result to the SC plank. Utah, Cal, and Auburn produced 1st round QB picks. If Cassel had played for Akron he could have been drafted 4 rounds higher or UConn that would have been two rounds higher. Two Pac 10 starters were picked ahead of Cassel, so starting in the same league for another team would have been better in the 2005 draft.
Do you know how many SC QBs rode the pine over the past 10-15 years?
As for his success with the Pats, it's very difficult to credit all of that to SC. And, even if you did, how could you posssibly credit Pete Carrol with more involvment that that of Lane Kiffin. That's really the irony of this whole debate, whatever credit you give to SC for QBs, one must consider who coached those QBs. It was not a defensive-minded head coach.