I've always wanted to damp a pair of Beats, especially because every pair I've tried had the cups literally rattle, which is a sign of shoddy plastic and damping. It'd certainly tighten the bass up if it had a nice treatment of dynamat or something. Cutting out the grill in front of the driver would probably let the mids and treble free too.
You void your warranty. And with that cracking headband and loose screws, you can't afford to lose your warranty.