The two options on the AMS for ProductID are DF700 or DF600F, not DF600.These are documented in the V-Series Implementation guide for HDS located on NOW.
Switching between DF700 and DF600F is not something we formally test.However, I have done this several times without issue and yes, the data will remain on the array LUNs.If I recall correctly, I believe changing the array ProductID will cause the array to reboot also.
You should shut down the V-Series controllers prior to switching the ProductID on the array.
V-Series + AMS arrays expands the usefulness of the array as you describe.The Array may not support thin provisioning.But using a V-Series with the array does support NetApp thin provisioning.
This same logic also applies to say heterogeneous replication between array tiers or array vendors.If you have a HDS AMS array and want to replicate to another vendor array, you can install V-Series at each location and use NetApp SnapMirror for replication.