I think this is like crafting. It can be worthwhile, but it has to be implemented carefully. I don't think it will ever be implemented because of the pay to win aspect of paying real money for items. I think Pay to Win skews the game balance, like many mobile games. Hows this for an idea: Implement a vendor that you pay an exorbitant amount of gimmer to (5,000-10,000 and maybe even rare materials like shards and energy) and he will give you a list of 2-3 items that he will trade you for your item you want to trade. This will be like the almighty Rahool and you will probably not get what you want, but each item could have a table of like 15 items it could be traded for. The odds you could get what you want are slim but you will still work hard for the ability to trade it and you could still maintain that sense of accomplishment that you achieved something in the game. Essentially its trading to the game and not to players.