I don't know how many of us were disappointed when our weapons that were pretty good at 99 that took awhile to make, are now lousy for post 99. Here's an idea I have to make these weapons useful for post 99 content again.
Melee Weapons:
99(104): Add +4 DMG, +4 Acc, and +25 weapon skill for that weapon type.
99(109): Add +8 DMG, +6 Acc, and +50 weapon skill for that weapon type.
99(114): Add +12 DMG, +8 Acc, and +75 weapon skill for that weapon type.
99(119): Add +16 DMG, +10 Acc, and +100 weapon skill for that weapon type.
Pet Weapons: (Add +2 to pet parameters depending on weapon per upgrade as well.)
99(104): Add +2 DMG, +4 Acc, and +20 weapon skill for that weapon.
99(109): Add +5 DMG, +6 Acc, and +40 weapon skill for that weapon.
99(114): Add +9 DMG, +8 Acc, and +60 weapon skill for that weapon.
99(119): Add +13 DMG, +10 Acc, and +80 weapon skill for that weapon.
Magic Weapons: (Add +2 to magic parameters depending on weapon per upgrade as well.)
99(104): Add +1 DMG, +4 Acc, +20 weapon skill for that weapon type, and +10 magic acc skill.
99 (109): Add +2 DMG, +6 Acc, +40 weapon skill for that weapon type, and +15 magic acc skill.
99 (114): Add +3 DMG, +8 Acc, +60 weapon skill for that weapon type, and +20 magic acc skill.
99 (119): Add +4 DMG, +10 Acc, +80 weapon skill for that weapon type, and +25 magic acc skill.
If you want to add your own input, like if these parameters are too weak, please just post what you think it should be, going by currently available post 99 weapons.