There are a few errors with this design. I don't suppose you really have the items set up like this in a working body model.
You need to consider several mechanics of the game as well.
For a part to connect properly, its parent must be added to the tree before it. So the abdomen that connects to the SPLEX won't work unless you will have SPLEX put before it.
For a part to be protected with armor, it needs to be a [LIMB] part. Specifically, I think Toady explained, that UBSTEP counts LIMBs going toward any GRASP from UPPERBODY, and LBSTEP counts any outgoing LIMBs. And LIMB happens to allow grabbing with the part when wrestling.
For a part to be individually targetable, it must have no SMALL tag. INTERNAL does not prevent it, and does not mean damage passes to it - SMALL means part receives damage from parent, and INTERNAL means it only receives that damage if it is critical.
There's no way to make a small part pass damage to its children, so a SKULL is of no use, since it won't prevent the brain from being damaged.
Damage to any CIRCULATION means certain death. So an abdominal aorta is bad in that regard. Also, why is the bladder marked circulation?
So, consider all that. I've been constructing such body designs periodically, but settled for what I have in my mod now as the most viable currently. The biggest problem of your design is unrealistically small target areas, such as the solar plexus as a separate part.
You did give me an idea for more spectacular arm losing in combat though, regarding torso sides. I'll check it out.