Security: Adding a layer of security on a per-filesystem basis is not sufficient or necessary. It is only conceivably useful as a backup plan when the actual security system has failed, and at that point it is not sufficient to prevent compromise.
Stability: Quotas are a superior solution.
Speed: Not an issue for /usr, which is rarely written to.
Integrity: We have journaled filesystems now. If you lose a filesystem it is almost certainly because the device has gone bad and needs to be replaced. For last-ditch system recovery, an initrd solution like Dracut works better, since it can solve problems involving the root partition.
Size: Modern computers can boot from any size partition.
fsck: Preventing fsck is no longer useful. It doesn't take an hour like it used to. If there was a power interruption I would prefer to fsck all my filesystems anyway.