you can set a system default using gconftool, removing 10_gnome-session is of no use until you run update-gconf-defaults, like the schemas the defaults are used only at installation time to write values in the system directory
you can set a system default using gconftool, removing 10_gnome-session is of no use until you run update- gconf-defaults, like the schemas the defaults are used only at installation time to write values in the system directory