What I did not see in the Weapon Designer rules which I would have like to have seen is some mention of dealing with weapon master bonuses. Currently 1/5 of Skill doesn’t really do anything once you get past size +3 or so.

You mean adding Skill/5 to damage? No, it’s not mentioned in the Weapon Design System, but elsewhere in GULLIVER are notes that such absolute damage bonuses only scale properly when replaced with percentage bonuses. So if each Skill/5 added, say, 20% to damage, or if you used GULLIVER’s suggestion for Karate damage bonuses (each skill level over 10 adds 10% damage), that would get the effect I think you are looking for.