They could always do what they did in Phantasy Star Zero. Like voidwatch everyone got their own chests but every chest contained the exact same items. So if one person opens there chest and gets a tefnut wand and a divine log. Everyone esle who opens their chest will get the same exact item.

Also before you go to the it won't work becuase then to many people will get 1 item at once especially the items that can be sold. Think of it this way, instead of 18 random chances of getting an item, you get one chance of getting an item then the results are multiplied by 18.