I’ve had this idea rattling about in my head for a long time. The basis for this life-size, life-weight dummy would be a burlap or canvas sack filled mostly with saw dust. The limbs and head would be solid wood. Inside the body would be a network of chains and armature that would make the marionette move only the way a slack human body would move.
For example, when you or I tilt our head to the side very quickly the should that we are tilting away from starts to rise, lifting the arm a little. If the head of a doll is just affixed at one point, perhaps as a socket joint like many popular dolls today, then it would be incapable of moving the way a human can. Though the plan for this dummy has a solid piece of wood as the neck, it is joined in the sack of the body to chains that anchor it to the ‘rib’ armature in three places making sure that it’s movements are connected to the movements of the chest and arm area.
This is only a snippet of how much I’ve thought about the mechanics of this thing. And, as a full blown project, a life size project, I think it would creep me out too much to ever make it. Though, perhaps a small sized mock-up?