You could set up a softlink to redirect the /dopusdata folder to a folder on the NAS.
(/dopusdata is an alias which will normally point to C:\Users<Your Name>\AppData\Roaming\GPSoftware\Directory Opus on Windows 7, but just type /dopusdata into Opus and it will take you to the appropriate location.)
I am not sure how well it would work as I haven't tried it, but in theory it would be the same as using Opus in "shared configuration" mode (where multiple users on the same machine all share a single config directory), so it should work.