Yeah i think if you make it less spherical it will look like an elbow hinge. Unless you really do want it to be able to swivel in any direction, but probably not.
I guess I shouldn't say it's ALL in the body language. But you can do a lot with that. Animated faces never have the same life that real faces do so getting the body to help is useful. Good taste should rule, it can get corny either way.
Watch some silent dramas made before , say, 1920 (like Rudolph Valentino in "The Sheik") and you'll see some pretty ghastly body and face acting.
On the other hand someone like Clara Bow had an amazing face that could say sentences without speaking. We don't think of her as a pantomimist like Chaplin, but she knew what she was doing.
I just looked at that Bow clip again and it occurs to me that between the lighting and the makeup her face has been simplified down to not much more than the mouth and eyes. Geez, in that last shot she's practically a panda bear! If she can work with that I suppose our robots can too.
If you have a chance to watch a Clara Bow movie she is a real study piece even in the weak ones.