Is it possible to write a script that runs at login which will automatically run a custom session for a given user? I would like to have my personal user account login to my normal, entire KDE desktop, and then I have another home theatre user that will boot into a single fullscreen application, Plex, by way of writing a custom session - with no desktop environment accessible until I logout and back in as my personal user. 
How can I set different sessions to be used for different users?
x11;login;session