You could perhaps have a limited number of \"skills\", and within those skills, a number of \"specializations\". Let\'s say you wanted to learn the sword skill. After you reached a certain level of expertise, you would have the option of continung to learn the basic sword skill, or you could choose to specialize in a particular style of swordfighting: longsword, shortsword, two-handed sword, etc.
For bow-fighting skills you could specialize in longbow, shortbow, or crossbow; for thrown weapons you might have sling, dart, knife and axe.
Some skills would not have specializations (knife-fighting?), but if new skills are developed that are similar to existing skills, they could be added in a tree structure instead of expanding the base list of skills. And this does not have to be limited to fighting. Cooking skill could be subdivided into baking, open-fire cooking, and bread-making, for example.
Players who coose not to specialize would continue to advance their skills acording to the basic rules for their type of weapon. Players that specialize would receive bonuses when using their preferred type of weapon, but suffer a penalty if using a different style of the base weapon. For example, someone who chooses to specialize in two-handed swords would do extra damage with their two-handed sword, and strike more quickly, than someone at the same level who did not specialize. But that same person would be less accurate when using a regular sword than the non-specialist, because they are not accustomed fo fighting with finesse.
