Mouselook in its current form is a bit limited and doesn't support right-click etc.
I suggest a new parameter be added to llSetCameraParams.
CAMERA_FOLLOW_MOUSE - TRUE/FALSE
toggle mouselook-like mode
and perhaps
llShowUI(integer value) - TRUE/FALSE
TRUE - normal userinterface, FALSE - userinterface like in mouselook
Basically, a bit like llForceMouselook with more capabilities. So what this should do is make the camera follow the mouse around and make the avatar move in that direction, like when in mouselook. This will make it possible to make customized mouselook with the possibility of scripted camera control and support for UI menus.