Thats great you are adding some commandline support.
Like the OP I have also used mpd and found it great for mangaing my music with a remote, though the frontends are lacking compared to MusicBee.
I have been using Foobar2000 since I made a switch back to Windows and am now re-evaluating different players yet again.
I am using a Harmony One remote with eventghost and for the basic tasks (play/next etc) use multimedia key mappings and the global hotkeys in the music player. But I also have buttons setup on the LCD to change genre, which I was achieving by using a different playlist for each one.
So I am wondering if it would be possible to add a commandline to select a playlist
Even better would be a "search" command where I could use a query string to add the songs to the playlist, eg /search "Artist=Blah OR Artist=Blah2", then I could create whatever I wanted on the fly, but I assume this would be a harder feature to add.