For the Mezzmo PC Client / Server it would be nice to have a Playlist functionality to queue up / remove selected content to play, and maybe some other functions like shuffle playlist, random play, skip recently played in xx days, play once.

and to further build on it you could have multiple playlists like Playlist1 will play to VLC Player on 192.168.1.1, Playlist 2 will go to Bubble UPNP on 192.168.1.5 ...etc