gnome-control-center depend on gnome-session for a DBus service only, the dconf schema is provided by gsettings-desktop-schemas. The gnome-session package is for people that want the gnome session management while gnome-control-center just provides a GUI for the gnome-settings-daemon settings. There is no compile-time or runtime blocking errors when dropping gnome-session. It would be pleasant to drop this "useless" dependency to allow people to use the gnome stuff they want. Reproducible: Always
Sorry, we can't do this. For instance, suspend/screen lock inhibit are managed by gnome-session. gnome-control-center and gnome-session are core deps of GNOME. Not using them both together is unsupported.