Allow changing camera parameters while in and out of mouse look relative to avatars position. These changes would stay relative to the avatar and allow the use of mouse look for experiences such as flashlights, weapons, etc.
I am personally looking to create a flashlight as an experience that changes your camera to an over shoulder view, and when entering mouse look the view stays the same, but allows further interactivity with mouse controls.
You could also make a third person weapon that affects your camera in and out of mouse look. Entering mouse look would enable shooting functionality, but you could still maintain a third person view.