and have a cap of (I think) 53 players. So from a "safety" standpoint, I would think DI (including DI-FCS) could reduce down to 53 without significantly increasing the risk of serious injury.

Plus, if DI-FBS reduced its number, then would DI-FCS have to reduce its number too? I ask because if both subdivisions are offering the same number of scholarships, then is there a reason to have 2 subdivisions for DI football? After all the only reason for the 2 subdivisions is because schools wanted to offer a different number of football scholarships.