The documentation for the Edge appliance installation is a bit vague on whether the storage for the edge device (additional storage after install), needs to be local storage.
The LUN management guide talks about the requirements for installation, but can data stores from other parts of the vSphere environment be used for storage, or must it all come from that dedicated ESX host?
If you're asking will it work, probably. If you're asking is it supported, probably not. Could always file a PVR and see what they say.
From a sales perspective, thats a vseries use case.
From a technical perspective, the VNVRAM implementation is based on getting a low latency ack from a local raid controllers write back cache. Adding a round trip to the EVA will add that latency to every write IO hitting ONTAP-v. If you had a supported internal array, even if it was just a mirror, you'd be in better shape. The VNVRAM is (almost) never read, it just has to journal that write somewhere before it can ack it so ideally it would never leave the write back cache anyway. So VNVRAM could stay local and data aggregates could live on the SAN, but support is another issue entirely.