Hopefully this is a simple request, and one that others will see the merit in too. Essentially, the media center users in my home will typically all be sharing the same "Movies" and "TV" libraries, and only our "Music" libraries will be different.
Because of this, I think it would probably be ideal if the server allowed for all users to use the Default Library (which I would define to include "Music" and "TV") and then be able to add custom libraries on top of that.
I do see that this has been requested by one other (jj12345) as well, but it was in a post that included multiple items, so could have been overlooked.
http://mediabrowser.tv/community/index.php?/topic/1452-media-library-management/?hl=default