This question is two fold.

Part 1:

Is it a bad idea to virtualize a storage solution and run VMDKs off of that as opposed to the original VMFS datastore.

Essentially lets assume I have 2 TB worth of RAID'd DAS. Currently I have a few VMDKs on the DAS VMSFS. What I want to do is remove the VMDKs off the VMFS, allocate a good 1.8-1.9TB for a FreeNAS installation (a big FreeNAS VMDK), and run the other VMDKs off of that via NFS.

I don't have the hardware for a NAS but have a bunch of different shares. This would simplify my management. I understand there is some overhead with another layer of storage abstraction (A virtual ZFS file system over NFS backed by RAID'd DAS formatted as VMFS) but I don't see how it could be too bad. The NAS also has more features than a simple VMFS datastore on DAS.

Part 2:

VMWare frowns on long running snapshots, but what about ZFS snapshots? Is it safe\recomended to run my guest VMDKs (Windows clients, random servers) on ZFS snapshots? This will give me the ability to quickly rollback VMs to earlier states without the implications of long running snapshots directly on the VMFS.