Today I started to design the body part system. Until now I had only body part enums, but no other code or plan for them. I'm using same kind of modular class/type for body parts as for many other game object sub-systems. The problem with body parts is the fact that not all creature types have same kind of parts, but I believe with careful planning it's possible to create a flexible system which doesn't need a lot of special-case code spread everywhere.
I plan to restrict the use of body parts mainly in situations where a certain type of damage is subjected to a body part. I think usually body part system is too detailed, but in this case it somehow seems to match the armour system where each body part can be worn. Later it could be possible to direct the attacks of creatures by the size or other special ability of the creature.
I really like to work with restricted type-style classes. It's possible to do game design in that level also and you don't have to worry so much about interactions with other types of data.