I'd love to have Playlist-related shortcuts, like being able to immediately play a song, or enqueue right after this one,  by clicking any of all available mouse buttons in the  song in the collection or playlist, with any mouse button, like clicking the scroll wheel button or one of those fancy side-buttons.

It would also be useful to remove a song from the collection with a Global shortcut...  Sometimes you want to add complete albums, but when you hear certain songs you want to remove them forever with a simple global shortcut, like the opposite of Love this Song, Hate this song (and remove from the collection... but  still don't delete the file). How easy is it to create new shortcuts in a script anyway?

How about making columns movable?  I would like to have the Current playing thing (with lyrics module, etc) on the left column, collection in the middle and playlist on the right. I would also LOVE to have a HUGE album cover, how about making the Current song module resizable to get a bigger cover?

When I was on Windows, eJukebox was my absolute favorite Playlist manager, perfect for parties and touch screens, you should look into it for inspiration. http://audiosoft.net/