Locking Playlists

It would be really useful to have the ability for users within a certain permission group to be able to lock playlists to prevent new submissions to it. If, say, Editorial needs time to cut shots onto a Baselight before a dailies session, or if a set of client submissions need a lot of paperwork to accompany them, it's useful to be able to draw a line under a list and know that no-one else will merrily be adding shots to it.