User blog comment:KodachiZero/Why Trading is Bad/@comment-26973445-20151211172846

Forget the trading, I think they should implement a limited summon event. In this event you will use 6 gems to summon. However, 3 random, different units will be displayed, and you are able to chose only one of them to recieve. This leaves in some randomnes and reduces the chances to summon a unit you already have.