Feature to assign id numbers to mp3player (additional theme parameter?)

Issue Summary

It would be really handy to have an easy way to assign an id number (ie. id="mp3player_x") to each MP3 Player object.

I am loading multiple mp3players using AJAX callbacks, due to this it's assigning id="mp3player_1" to all of them. At the moment I am doing a messy string replace on the html returned in order to assign a unique id, before injecting it into the DOM.

Perhaps this could be an additional parameter in the theme function, unless someone has a better idea?