On Wed, 19 Sep 2012, Scott Ritchie wrote: [...]
There is one major snag, however: unionfs displays the owner as root until the user has modified/copied it. This means Wine refuses to launch as the user with the "root-owned" prefix.
Wine checks the ownership of the $WINEPREFIX directory right? So wouldn't touching a file in $WINEPREFIX before starting Wine work? system.reg would be a good candidate. Alternatively, create/delete some other file.