Runescape style would fit this perfectly as long as there's limits as to what you can trade. Example exotic or some raid gear. Because trading raid gears a good idea to extent but it would be wrong just it give someone a hole set. So imagine you could trade one gear every one raid. so if you don't get that gear but your friend Did who doesn't need it, you can trade something they need like shards for a legend like a legend for a legend. That's my idea tho I mostlikly missing a few things leaving loop holes but the ideas there.