Facial animation concept

This here is a very small test I made to show how a mouth might work for this character (right click + save as on the picture). The idea is that most of the time there will be no mouth, and it will only pop up for stuff like fear or laughter. Don't mind the actual animation, it wasn't meant to be perfect.
The "facial rig" is very simple. Most of the animation is done with free Translation/Rotation/Scale animation. There are a few morph controls for the mouth, and one squash/stretch control for the whole face, just to make it feel a bit flexible.