So, after installing SI2013SP1 I finally got around trying to relocate my user folder to a different drive by changing the XSI_USERROOT variable to point to a new location in the setenv.bat. This did seem to work, however now all my addons and plugins are listed in the plugin manager with their full path as if loaded externally, not as belonging to the user folder. So I am probably doing something wrong... Please enlighten me...
And as an aside (formerly its own thread), that comes up after every install: Why does Softimage copy existing addons to the "installed addons" folder, when migrating preferences, but seems to make no attempt to install them, even after restart? This way, I'm forced to move them out of the "installed addons" folder again, before drag&dropping them back into SI, otherwise I get a "is already installed" error, although nothing has been installed yet... Again: I'm probably missing something here...