Minecraft Trading Plugin

Hey guys, I have recently made a MA, and I use the plugin http://dev.bukkit.org/bukkit-plugins/shopkeepers/. I like this plugin, but I have an issue where, it only does villager trading. This is a problem because I would like to have, persay, the ability to trade 2 items for 2 other items, and normal villager trading doesn't cut it. I have tried plugins like Citizens 2, but found no character trait that allowed this. Is there any plugins I am overlooking? Is there a way to do this with citizens?