Frederic was on-the-mark here; most/all desktops currently use some mechanism for
specifying 'startup programs' (outside of the existing 'sessioning' mechanism). The
full-blown sessioning/save-yourself protocol of course requires client interaction, etc. but
this request isn't about saving state, it's just about adding a client to the exec list.
I am saying that we need IMO a standard mechanism for doing this (i.e. what gnome does with session-manual and KDE does with autostart) just as we are working on a standard sessioning mechanism.