I think that as trading is out of the question, and that you don't always get items that are useful (even if they are mythical
), that there should be a way to swap items of the same rarity, not with other players, but with the shop. There could be a set swap available each day, such as Needle Blaster for Super Nova, say. This system eliminates the problem of people swapping their mega rocket storage 1 for a needle blaster. To get a trade (or swap) you wanted, you would have to wait until the one you wanted became available. Also, each category of item would be kept separate, so, for example, if you had a mega rocket storage module and you wanted an Ultraspade, you couldn't do it. This would (hopefully) be a better way of implementing a way to get mythicals you want.