Other why not ZFS(raw)+HAST+CARP+iSCSI ?

I read these Thread 29639, Thread 38397, Thread 50325 before starting a new one.
Why not consider creating ZFS zvol with volmode=dev then give them to HAST, adjust devd script to failover CARP IP and finally start iSCSI Target ?
Is the order in the thread title looks fine or not ?
Each configuration puts ZFS after HAST with problems after failing master node to import ZFS pool to new master node. I do not want ZFS heavy tuning, there are threads dedicated to this, just to be able to use lz4 compression and give LUNs to a virtualisation platform with redundant storage servers.
I have several FreeBSD 10.[23]-RELEASE running well with CARP and net.inet.carp.preempt=0 and have no problem of auto failback, but I just have one IP on these couples of server. It would be more complicated with several CARP IP...
Thanks for any comment !