Just an idea for a new skill mechanic, partly based on the discussion about variations of the Weaver skill to make clothing, hats, shoes, gloves, etc.
Specialties are specific applications of an existing skill. Tailor is a specialty of Weaver allowing you to craft clothing but not baskets or sails… Leatherworker is a specialty of Armorer involved in making leather armor. Specialty skills are always named for occupations, same as skills—Trapper, not Trapping. Calligrapher, not Calligraphy.*
Specialties for Fighter, like Axe-Thrower or Sword-fighter, are specific to a weapon and/or use of that weapon. Similar specialties in different skills don’t stack (e.g., Bowhunter and Archer; Liar and Grifter).
Benefits: The benefit of a specialty is that the obstacle is reduced by 1 when performing that skill for a specific application. Obstacles cannot be reduced below 1. You may only possess one specialty per skill.
Requirements: Gaining a specialty requires the normal number of passed tests to advance, but no failed tests are required. Tests toward gaining a specialty are tracked for that specialty—they do not count toward the root skill. You may only train toward one specialty at a time—if you switch tracks, reset those tests for advancement.
For example: I have Hunter 3 and want a specialty in Fisher. After four passed fishing tests, I gain the Fisher specialty. I still need four passed tests and three failed tests to advance Hunter to 4.
Someone with a specialty can use the Mentor skill to train another character in either a skill or a specialty. Even the Mentor skill may have a specialty (for example, an Alchemy Professor could teach Alchemist).