It sounds like you're just getting an advisory message (which James says he'll remove). If the "play song" command is working for you and you use it a lot, the options are to either cope with the loading time or find a filtering method that's appropriate for your situation. It doesn't necessarily have to be by rating.
Coming up with a filtering method that's appropriate for your situation *is* the best method of optimizing the loading. (You can also turn off subset matching for that particular payloadXML, if you haven't yet. You'd then have to say the complete song title for the play song command to work. That is also a form of optimization.)
I just noticed that James provided another possible way for you to filter your songs.xml the other day, based on play count.
http://voxcommando.com/forum/index.php?topic=1325.msg11411#msg11411Why not try that for a week or so, and see how much it impacts things before deciding it's not an option?
If you're regularly asking to play songs that have never been played before, it will quickly become obvious and you'll know it's not the right solution for you. But if it ends up happening only rarely, in those cases you ask for the artist or album in order to find/play the desired song that one time, and then it will be added to your played songs list in short order -- problems solved.