I just wanted to make the same wish..
I found the function I want in the context menu of a song: RMB -> Play More... -> Output To
and I'd prefer to have this device list near the play button or the loudspeaker symbol of the player.
In my opinion, that's where it belongs since it applies to the current playback and not to one song.
Also, nowadays it is not uncommon to have more than one standard output device so that functionality became more important over the last years.