You need to create external .exe application (tray application) which kills and restarts SolidWorks like Terry suggested. Important that this .exe should be executed as separate process (Process.Start/Shell) within the add-in so it is not terminated when the add-in unloaded.
Artem Taturevych, Application Engineer at Intercad (Australia)
translationXpert – add-in to translate SolidWorks models
myIntercad – an integrated tool for SolidWorks Professionals