/signed
I'd go one step further.
Put NPCs that can:
1. Strip all mods, giving you a clean weapon for a small fee (500g?) Or, alternatively, sell generic mods cheap that will replace exotic mods. For example a generic "bow string" you can buy cheap so you can replace the crappy 1:1 vampiric string that ruins an otherwise perfect bow.
2. Recover all mods, destroying the weapon for a larger fee (2k?), if you dont want to pay you can always take your chances with expert salvage kit.
3. Trade mods. Those mods that come in multiple values will be available as perfect or -10% of perfect. If you sell a mod that is not perfect the NPC buys it as if it was a -10% of perfect item. If it is below -10% of perfect, it buys only at face value. (to avoid having too many things to scroll through)
4. To avoid panic buying and selling, perfect health and energy mods should start at 10K, perfect vampiric, defense, sundering, warding, shelter and enchantment mods should start in the 2-5K range, everything else (poisoning, zealous,elemental, and 10%+1 attributes) can start at the usual 250g. Prices of course will adjust based on supply and demand.
A

