Ive never used A6, so you'll need to to a bit of research on HOW to implement,
this but here is a concept that may be managable in A6.
1> Get the vertex nearest the 'impact" point.
2> Get the UV co-ordinate of that vertex.
3> Get the COLOR of the pixel at that UV co-ordinate from an unused,
color-coded skin(that is embedded in the MDL file). These colors relate to
which limb / body-part is in the actual uv-mapped skin.
4> From this color you know which body part was hit.

Get what I mean? Have a second, never-displayed skin with simple colors
painting the different body parts.