How about, if the client has "avatar in Mouselook" checked, we can have a new state in LSL...
llSetStatus(STATE_VISINMOUSELOOK, TRUE);
Of course, if that option was unchecked, it would do nothing.
Anyway, this would be infinately useful for making "Heads Up Displays," because, as of now, objects attached to the head (yes, anywhere in the head) don't show up in mouselook. Apparently, it's a feature.
But sometimes, I wouldn't want people to see attachments on me (like big costumes) even if I want to see my avatar, or other attachments (like the heads up display, maybe).