I would like to disagree with you. You can detach it but, not use it as a seperate moniter. You just take apart the emac and remove the wires to the monitor. If it is screwed on remove the screws and there you go a detacable screen.
you for sure could unhook the monitor connection inside and use only an external. would the video mirror port then work as a normal monitor connection? I wonder this because mirroring is usually limited to the max res of the built in screen.