I've never tried this, but I strongly suspect it cannot be done.
The VMWare Tools inside the VM "fake" network access to the host as evidenced by the fact that you can still access the host (via a UNC path) even if the VM doesn't have network access.
CSC.sys is a low-level system driver that sits at the same level as the network stack. I suspect it loads first so it can do it's thing, and it's smart enough to know the difference between a local volume and a network path (even a "faked" one), since that's the whole point of its existence. The cache location is supposed to be a place of guaranteed access in the event of a network outage. The parameter exists only to place it on a different local volume in the case of a space-constrained C: drive.
Placing the cache location on a network drive (even a faked VMWare one) would be ripping a hole in space-time continuum as far as the OS is concerned. This is probably why Windows won't boot when you try. No one would've thought to correct that bug since it makes no sense (after all, you could theoretically isolate the guest and/or uninstall the VMWare Tools and you'd lose access to the host's volumes as well).
Also, NTFS junctions are not as robust as *nix hardlinks and symlinks are. There are lots of programs that aren't fooled by them. Even Windows Explorer didn't know what to do with them before Windows Vista came out, and the only reason that got fixed was because Microsoft started using them for compatibility with Windows XP.
If you actually manage to make that work somehow I'd love to know how you did it.