-1
If you have diamonds and want emeralds, just sell your diamonds and then by emeralds with the money. Trading shops would be too specific, if you just use meebles you can use the money from anything to buy emeralds, not just what the trading shop specifies. Trading shops would hinder trade, as people would have to find specific items just to use them. Also, items take up inventory space, while meebles don't. If you want to buy a large amount of something from a trading shop, it would use up room in your inventory and might even make it necessary to make multiple trips. Overall, it just seems inconvenient and not really a useful addition. It doesn't accomplish anything that can't be done a different way.
Also, techs probably have more useful things to work on than this.