Don't forget too the face controls respond to all transforms, rotation, translation and scale. Try twisting them, and translates (Remember the translate is a bit weird, hold down the [esc] key while dragging)

If you do need to add bones it can be done without breaking the morphs but it will impact the scale behavior of the other chips ... Poser's scales are insanely complex and interact in ways you wouldn't expect. If you do add bones to the face just don't create new groups in the figure. That's what can break the morphs. A bone doesn't need to have a group. It does need Affected actors. In the Joint editor you'll need to make sure the head is it's affected actor. It should set that automatically. If you zero the scale weights maps for the new bone it will minimize it's impact on neighboring bones. But of course, it won't be able to scale.