ie, what would the manifests look like?

lets ignore the title for now, as that's not clear what it should be, but say:
 <dir name="apps">
                <dir name="gnome-screensaver">
                        <entry name="lock_enabled" mtime="1185841502" type="bool" value="true">
                        </entry>
                        <entry name="user_switch_enabled" mtime="1156540919" type="bool" value="false">
                        </entry>
                        <entry name="mode" mtime="1247684848" type="string"><stringvalue>blank-only</stringvalue>
                        </entry>
                        <entry name="idle_delay" mtime="1247685088" type="int" value="20">
                        </entry>
                        <entry name="power_management_delay" mtime="1247684943" type="int" value="60">
                        </entry>
                </dir>
</dir>


would something like this feel right?

gconf2 { "screensaver_lock":
  directory => "/apps/gnome-screensaver",
  entry      => "lock_enabled",
  value     => true,
}

gconf2 { "user_switch_enabled":
  directory => "/apps/gnome-screensaver",
  entry      => "user_switch_enabled",
  value     => false,
}   

gconf2 { "mode":
  directory => "/apps/gnome-screensaver",
  entry      => "mode",
  value     => "blank-only",
}

gconf2 { "idle_delay":
  directory => "/apps/gnome-screensaver",
  entry      => "idle_delay",
  value     => 20,
}

That all seems reasonable, what about:

        <dir name="apps">
                <dir name="panel">
                        <dir name="global">
                                <entry name="disabled_applets" mtime="1213038439" type="list" ltype="string">
                                        <li type="string">
                                                <stringvalue>OAFIID:GNOME_FastUserSwitchApplet</stringvalue>
                                        </li>
                                        <li type="string">
                                                <stringvalue>OAFIID:GNOME_FastUserSwitchApplet_Factory</stringvalue>
                                        </li>
                                </entry>
                        </dir>
                </dir>
      </dir>

gconf2 { "disabled_applets":
  directory => "/apps/panel/global",
  entry      => "disabled_applets",
  value     => [ "OAFIID:GNOME_FastUserSwitchApplet", "OAFIID:GNOME_FastUserSwitchApplet_Factory"],
}