I'm interested in this subject because I recently had an encounter with CryptoLocker ransomware and it was unpleasant. I thought if I could boot from an iSCSI device that was actually a zfs volume on a NAS4Free storage server I could use the zfs snapshot/rollback capability to quickly recover from such problems. I've gotten this to work when the iSCSI drive is used as data drive in Windows 10 but having it be the boot drive would solve a lot of problems.