slimserver is quite nice in some regards (yes, I’m outing myself as a Squeezebox owner here), but I still prefer mt-daapd over it. slimserver can’t even do utf-8 properly.
Anyway I agree that this would be the task for a separate client application, which would have the advantage of playing contents of any iTunes server.
By the way, does slimserver even play on the same machine? I thought it just manages playlists and controls clients, including the Java one…