I have to admit that I only skimmed the thread, but I'm still a little puzzled why you'd want your home directories to be put on UFS instead of inside a ZFS pool. Although those quotas I mentioned above work perfectly to help protect (and/or divide) the available space it is by no means comparable to the diversity and flexibility which ZFS can offer.To avoid /usr/home to be mounted after boot I used the command:
# zfs set mountpoint=legacy zroot/usr/home