You're correct, there's no VSS provider for Hyper-V at this time, though I believe it's on the roadmap.
I've never built out the configuration you describe, but if the deduplication function is an offline function that operates on existing data, then you could eat up a lot of unnecessary snapshot space on the Nimble system as the data gets deduped. This should theoretically wash out over time as old snapshots expire, but a lot of Nimble users have long snapshot retention periods so it may be a bad idea in that respect. But there's no inherent conflict between dedupe and compression like there is with encryption.
I also have agree with Kevin Hobbs' opinion that the additional layer of storage management is something I'd avoid. It sounds like this kind of setup is intended more for making direct-attached storage emulate shared storage, with a protocol switch (iSCSI to SMB3) thrown in for extra complexity. Troubleshooting storage problems could be really tricky.
But if it works well for you, please keep us updated. Always glad to learn new ways to do things.
Hmm I have a bit of the same feeling regarding levels of complexity, and would prefer to not ad another level.
On the other hand the issues with storage will either be from the SMB servers to Nimble Storage or from MS Hyper-V to MS SMB and not from Hyper-V (CSV) to Nimble... That's the support type can-of-worms I rather not fall into.
We are having our startup meeting this friday so I'll try and update this page.
I'm starting deployment of our first Hyper-V cluster and face the same decisions. Using SMB shares for vhdx storage makes the hv hosts simpler (no multipath etc). And you can mix and match different hosts without worrying about storage. For the partner, this is a good solution because everything from the SMB server up is the same for all customers. Only the SMB cluster has the storage complexity. But, and it is a big one, that adds a very complex link in the chain. That thing better be resilient.
I'm opting for direct iSCSI connections from the hv hosts to Nimble. It means dedicating nics but that's life.