So 'shuffling' won't work too well because you need to restart game to hear new song, but you could run a script to pick a random mp3 in a specific folder and overwrite your current combattheme1.mp3 in your p99 folder.
I wrote this script to work with node.
You could then have this script run when you run eq so that it would change your combattheme1 each time you launch the game.