I tried working on making a power menu button that would toggle the orientation lock (which isn't exactly the same thing as this, but it's relevant), and never managed to get it to happen without having an x-term launch for a moment.

ANYWAY: power menu is part of systemui, if I remember it right. And systemui is closed source, if I remember that right. So ideally someone would just recode the entire systemui thing, and then we could add more configurable features to the clone.

Alas, that won't be happening any time soon.