After mirroring the "Shapekeys" in preparation for the rigging of Piero's "Facial Shapekeys" a quick "Preview Rendering Screenshot" in "Cheek Suck Pose":
With a "Corrective Shapekey" for both eyelids on the left side and some further tweaking I get this:
The "Corrective Shapekey" is still active on the last frame with an "Influence" of "0.176" because the eyeball would otherwise pierce through the eyelids on their way to the maximum opening:
My "Parabolic Function" looks like this:
(-(((var*2)-0.59)*((var*2)-0.59))+0.33)*3
A graphical representation (sky blue curve) and the intermediate steps for creating that curve:
Just a quick "Cycles Preview Render" snapshot with a test of the "Shapekeys" for "Cheek Puff", "Mouth Corner", "Inner Eyebrow", "Middle Eyebrow" and both "Eyelids" on Piero's left side:
A new bone added for the upper beak and some new "Custom Bone Shapes" as well:
Piero's rig is now complete and ready for animation:
There're 438 bones in total .