i dont believe that it would be too difficult to implement on anets side and it would do a lot of good in decreasing spam and saving time for both sellers & buyers.
there would still be a player to player trade market for the more popular mods [ie. +30hp, 20/20ap etc.] just like theres still a player to player market for superior vigor runes but people who dont want to spend countless hours trying to sell a +5nrg staff head for 500g or equivalent can just go to an npc and merch them for a decent amount of gold.
i cant think of any reasons why people would be against this idea so just /sign away
