I have been exploring the custom NPC's and a little bit of industrial craft trying to sort out how I can set up the trading system for my year 10 maths project. The other night, while I was supposed to be doing 'other' things I started messing around with NBT edit and normal villagers and WOW!
The idea first came to me after watching some youtube videos, where a couple of people were playing a custom adventure map and the villagers in this map had custom trades. So I had a play with the NBT tags on villagers. The NBT tags allow me to make custom trades, giving a heap more options for trading then either the custom NPC's or industrial craft can provide.
The main advantage comes from the ability to have 1 or 2 'selling' items for 1 buying option. Whereas I am pretty sure both custom NPC's and the industrial craft trade'o'mats have 1 for 1. The main disadvantage was that the villagers would generate new trades that I did not want them to.
However after a bit of googling on villager trading mechanics I have found a remedy for this issue. Villagers only generate new trades if the 'last' trade, all the way to the right is used. So if the last trade never gets traded, or is impossible to trade, no new trades will be generated. So I am pretty sure I will be using the standard villagers for trading, and the custom NPC's for dialogue.
Oh and on a side note, you can name normal villagers, choose their profession and even make them invulnerable. So I need to get designing my economy, the prices for items based on the coins from MystCraft. I am basing my calculations off a full economy and price guide I found on the Minecraft forums, here is the link to the post http://www.minecraftforum.net/topic/1237888-working-outline-for-a-balanced-server-economy-v10/ and I will upload my spreadsheet when it is complete for anyone to use if they would like.
Thanks for reading, feel free to comment below, and one day soon I am going to record some more tutorials explaining all of the neat new features we now have access to in MinecraftEdu.