While in the long term, that'd be great, I think part of the problem is that damage isn't very well modeled, or at the very least, not CLEARLY represented in current DF.
Right now, for example, it is possible to have a massive skull fracture and survive.
The real problem is that damage tends to be all-or-nothing. That is, it either does nothing of note or it fractures a bone or disables a critical organ. Pulping is starting to make this better, but there needs to be more gradient between when something is a massive laceration and a mere poke.
Again, it seems to be getting better with pulping, but in the last major version,
an unarmored human could be nibbled to death by three gerbils through the fact that ANY attack that pierces skin causes the same amount of pain, without regards to actual damage done. Hence, they give in to pain and slowly dehydrate to death as they are locked in permanent pain coma, in spite of no real damage being done. In essence, three gerbil nibbles on your toes would inflict three times as much pain as having a massive laceration across your gut that nearly disembowels you, because the three gerbil nibbles are three
separate attacks, even if they all bite the same toe.
Beyond that, there's organs that don't do anything yet, like the spleen.
Someone just posted
something the other day about "piercing" attacks always seeming to be aimed straight for the bone, rather than puncturing through muscle then back out due to being an off-center shot.
Then there's the fact that the new body types from DF2010 were so complicated that he largely copy-pasted the same body onto every animal because he didn't have time to properly give them all details. Hence, alligators are basically the same animal as a cow, but smaller.
In general, I think Toady intends to let things like this happen eventually, it's just that it's something he dabbles in only from time to time.