Yes its 3-3-5 and yes my "assumption" about defensive coordinators vs. position coaches, current players and recruiting coordinators is accurate. D - Coordinators and O - Coordinators only get involved if the recruit is someone they are promising playing time to (Katin Houser).
But you seem to be missing the point entirely.
First, 3-3-5 is dependent on communication, as cover changes pre - snap. A large part of the defensive underperformance in the first 4 games this year was simply players learning how to play and communicate a new defensive system.
Second, its during the bowl prep that BB formulates to following year plan and when the position coaches (and sometimes the coordinator) sit with the players that will remain on the roster after the bowl game to determine whether that player will be returning to Illinois.
Third, bowl season is also when the position coaches and recruiting coordinators worked the most hours. That is when the recruiting takes place. Why was our defensive recruiting weaker than normal last year? (1) we changed defensive coordinators and (2) We used the vast majority of the money allocated to defense on retaining our linebackers and defensive backs.
Finally, you ignore the economics. BB would like to stick with the defensive coaches and players we would have returning. Why? First, continuity - you don't want to use 3 defensive systems in 3 years. Second sticking with the current coaches and players, would be the easiest way to fill the recruiting gaps and the least expensive. You completely ignore the fact that BB admitted he didn't have the money to spend on D - Linemen last year. We change coordinators and then we have to change personnel and spend more money. Money which we don't have.