[lokum]

That sounds ingenious - will give it a go later and report back.

edit.  I've set it up with Kodi Callbacks so that when the screensaver is active it executes the builtin function XBMC.LoadProfile(profile_with_no_tv_client).  For that profile I've set the keymap for every key on the remote to XBMC.RestartApp.  I've set the default login to the Master profile which has the TV client active.  I did try using XBMC.LoadProfile(Master) instead of restarting Kodi but it was crashing.  This is a decent compromise.  Thanks -chris- !