It's been several months since this has been removed and no one seems to talk about it. I suggest that they be brought back since, other than endlessly mining, they were the only way to farm for Green Gems. I know it was removed due to a change in the Exotic Gardens plugin causing fruit to drop more than intended from trees. An easy solution to this would be to just change the numbers on the trader. Instead of 3 Dirty Gems/stack of fruit, just make it 1 Gem. 2x-3x fruit drops negated by getting 1/3 reward, comes up with the same numbers as before this 'bug'
omg yeah i have a bunch of fruit trees and I look for that NPC but couldn't find him. I think it should be added back with your solution.