An *.ini in a public location can solve the problem. If you have security concerns then make the launcher store its setting in the private folder.
User changes the setting: autostart:on -> autostart:off
client calls launcher with "-a Off"
launcher starts, saves the new setting in private folder, exits
Identical scenario for switching the setting on
Client and launcher communicate trough PS key. Launcher is always running and listening to key change events but can only read the value. Client may only write the value when needed so that the launcher reads and stores the new value.