It just popped in there when thinking of what the latest incarnation of an automaton would do.  The original ones played music, drew pictures in 2D, shot arrows.  A 3D printer based on a human figure would be the next iteration.  3D printers are really imprecise.  A human figure moving the print head would be even more imprecise.  The human's print head would move in an X-Y plane, the same as a 2D drawing.  The platform would lower to get the Z direction, thereby preserving some accuracy.  The X-Y position would be a kinematic problem using the arm.  A test arm could be made out of servos for testing X-Y positioning.  No way it would be accurate enough with traditional mechanics.