OK, this may be a bit of a niche case, but hear me out:
I prepare multi-channel backing tracks to use in Cantabile, either as simple left/right stereo pairs (backing left, click right) as MP3 files, or as multi-channel FLAC files, with the main backing in stereo and the click as a third mono channel.
Correspondingly, my media players in Cantabile typically have a stereo output PLUS a separate mono output (for the click)
When I add these to a media player in Cantabile, it takes quite a bit of tedious editing of Media File Properties to get them assigned to the right output ports initially:
It would be great to have presets to do this with an easy click - simply select an assignment preset, and Cantabile does the assigning for me. If the preset uses a source channel that doesn’t exist (e.g. assigning a three-channel preset to a stereo file), that assignment is simply ignored - done!
Icing on the cake: define an assignment as “default” for that player, and it’d save me even the effort of selecting the preset 
@brad: pleeeeease?