I have a vague idea for something. I am referencing the Armaments HR, which is based off of Lords of Men, both of which differ from C&G.
My idea is to add twice the bonuses provided by the weapon to the divider. And round down instead of up.
Items Produced = Craft score divided by 5 + (twice the bonus(es) provided), multiplied by two for Longswords. Donna, at a score of 15, can produce in a Season...
(15/5) x2 = 6 Standard Longswords
(15/7) x2 = 4 Superior Longswords (+1 Attack)
(15/9) x2 = 3 Supreme Longswords (+1 Attack, +1 Damage)
(15/13) x2 = 2 Excellent Longswords (+2 Attack, +2 Damage)
(15/17) x2 = 1 Exceptional Longswords (+3 Attack, +3 Damage)
(15/21) x2 = 1 Extraordinary Longswords (+4 Attack, +4 Damage)
15/25) x2 = 1 Exquisite Longswords (+5 Attack, +5 Damage)