there will be change in device name of /storage/seat (/dev/sdh)
Actually, that won't make any difference. They use LVM, so the actual device holding the volume is irrelevant. (only sda matters as that's the boot/root volume) But it's easy enough to put the new disk back at the same place.
I would say, just mark it "thin" and vmotion it. It won't actually use 1.4T.
