It shouldn't be a problem.
It doesn't meter what kind of logical volume you will create (NAS, iSCSI or FC), you are always able to add the "use volume replication" to such a logical volume. You don't have to reboot the DSS V6. The volume will be inaccessible only for a minimal period of time (<1min) when the options is being added to the logical volume. After it's added you can create a corresponding logical volume on the other node and setup the volume replication task any time you want.