iSCSI and FC Paths to Volume

Hey Guys, This is something that came up in my  Admin training on the Compellent, It  was told to us that you could attach a volume with both ISCSI and FC Paths to the array, and by using RR with Subset you can have the ISCSI paths take over in the event of a complete fibre channel failure and vice versa. Why this is of interest to me is for a san migration, I have a host attached to a different fabric with another vendors san.  Plan would be to attach a new volume from the compellent via ISCSI, Copy  the data between the two,  when happy data is valid disconnect from the old SAN, Cable to the new switches, zone to the compellent on FC, Add the FC paths and then drop the iSCSI, ***! online migration, But from all the testing have done over the last few days this does not look like it will work. I have a Win2012 R2 server attached to the SAN via iscsi  and FC, When I present a volume on iscsi and then add the fibre paths later it never shows the new paths on MPIO, Even after a reboot, Then when I disconnect the iscsi the volume disconnects and does not recover. Has anyone tried this? Is this even possible?

Any feedback greatly appreciated!

Thanks