I've recently tried editing entity_default.txt to include large daggers as a human weapon and picks as a dwarven weapon. As I expected, genning a new world with these changes allowed me to put points into Knife User or Miner during character generation in Adventure Mode. However, when I make an adventurer with most points in Knife User or Miner, the game starts me with a copper spear, a copper dagger, and no shield, just as if I did not have the most points in a weapon skill at all. (I also tried this with goblins, who have large daggers to begin with, but the same thing happened.) I was also unable to find a dagger-wielding soldier in any fortress at all, although I did find daggers for sale in human shops. It seems that the civs are unable to recognize daggers or picks as legitimate weapons.
I've looked through the rest of the entity_default file and the item_weapon file, and it doesn't seem that I have to change anything else to make humans use daggers and dwarves use picks—other weapons are used by civs solely by their inclusion in entity_default with a [WEAPON:] clause.
This raises the question: does DF contain hard-coded distinctions between "proper" weapons like swords and axes and other items like daggers and picks? Or is it a bug that I can't make civs use certain item types for weapons? Has anybody experienced the same problem? How was it in previous versions?