1) Build up the Stop Motion puppet body using Soft Sculpt method
2) Construct replacement hard resin heads or replacement facial features (like Jesus the Miracle Maker ) ..... or use molded foam latex or silicone skin heads (covering underskull) with animateable wire facial elements or small joints-levers-paddles underneath skin (similar to Corpse Bride)
So if it works ..... I can see were Soft Sculpting methodology is applicable for one-offs where you need only a few or one of a kind puppets. If it were a big production ..... where multiple or duplicate puppets required, then I think the molding and casting technique of puppet fabrication might be more appropriate.
"The secret to realistic
sculpting," says Lisa Lichtenfels, "is an accurate skeleton." Her sculptures
always begin with detailed drawings of the skeleton and musculature. To
create the skeleton, she molds 3/8" aluminum wire; when the skeleton is
completed its proportions reflect actual human anatomy and can be positioned
in any natural position that the human body can obtain. After wrapping the
armature in cotton thread she builds the muscles using batting which she sews
into place. Using nylon for the skin, she stretches it over the figures in
multiple layers which she will vary until she obtains the result she desires.
"Nylon is like no other fabric. It can be stretched to nine times its
original dimension, yet still return to its original state," states the
Topic at message board
Soft Sculpt Puppet Build-up: Fiberfill 'n Nylon