A little idea that a friend and I came up with while ranting about how the crown crates dropped stuff to each of us that we would never use because we don't play with the associated races.
I tend to play with plenty of Khajiiti characters and the occasional elf or human, but I can bring myself around to making an Argonian as I do not like the way they look nor do I like their racial passives. However, the randomness of the crown crates dropped Argonian hairstyles and adornment for me often enough to annoy me.
The idea came to mind based on me getting an Argonian specific drop that he really wanted, and that he managed to get a Khajiiti specific drop that I was looking to get my hands on, and that he stated he would be unlikely to ever use.
Such a trading system would really be just to correct style drops based on preference instead of pure randomization. However, such a system could possibly be implemented with the entire crown store to allow 'gifting' between friends and family, or trading other collectibles such as mounts with other players based on preference, considering that some collectibles never get used anymore because something more up to date and more stylish came along. This could also alleviate the disappointment that some newer players experiance when they hear about mounts or costumes that were only available for a limited time and that they may never be able to get.
It could be implemented as a standalone system for crown store item trade only or it could be implemented into the existing trading system by making it possible for collectibles to be put into runeboxes that would be tradable.
I suppose this is more of a public rant than a suggestion, but if such a system could be implemented, it would be worth consideration by the devs.