That is nowhere near as easy as it sounds. The problem isn't justification for developing it - there's plenty of demand! The problem is that the VM is running.
When the OS boots, it figures out the offset for partitions on disk, (along with a ton of other structures), and keeps all that in memory. Any I/O to/from a partition is relative to the offset. If we start moving blocks while the OS is running, corruption will occur as soon as the OS tries to access blocks that have been realigned.
This is why mbralign requires the VM to be shut down. The guest has to re-read the partition table, which it does on boot. There's no magic way to switch the disk and tell the guest that the entire partition just moved 512 bytes to the right.
Now, we're looking at clever tricks in ONTAP, but don't expect anything soon.