I'm also aware of Globalscapes Avail Agent.
Here's the catch.... even if you map the network drives.... Autocad mapping ignores them at the root level and sees paths as unc and that is where you are screwed, and deployments tell the tale.
ideally, i'd prefer 1 server and high performance accelerations over high performing fiberopt network connections and eliminate this bandaid cheaper than a good network solution.
I don't see the problem, I have all the drives mapped the same way in all four locations. We have no problems with xref's or anything.
Open the sheetset manager database and you will see that if the data base is accessed by multiple locations, the UNC path is changed to the local server regardless of the mapped drive path.
It does the same thing for anyfile kept on a local server, in fact, it changes the paths because it keeps copys of the xrefs on your local computer anyways, unless you tell it to do something differently....
AutoDESK hasn't changed how the paths work since the inception of arg files. The program is not designed to play nice with a complex network and the more you dig into the more obvious it becomes. You really need a Network or Software Engineer to customize your WAN, LAN, hardware and software in such a way that it replicates the program functioning with files retained "locally" i.e. on your c drive, like autodesk initially intended it.