What you are trying to achieve is currently not possible without writing custom code. Skeletal animation only affects the vertices of the skinned mesh but not the vertices of child objects. You would need a solution similar to SkeletonHelper.updateMatrixWorld() in order to animate the LineSegments (wireframe) object.
If possible, just set material.wireframe to true for the SkinnedMesh's material. But in this way, you get a pure wireframe and no overlay.