Snapshots (For VMs and shares) would be huge. Right now it absolutely stops me from being able to recommend this to even a small business.
iSCSI would be huge for me in a home scenario. Right now I run a VM on top of unRAID just to do iSCSI, which is an unnecessary pain.
A secondary array that uses ZFS is again something I have to use a VM for at the moment, which I would love to see baked into unRAID natively.