I would like to simply suggest that the PVP cosmetics that come out of the chests be available to be tradeable on rotation similar to PVE cosmetics.   
 

I feel the current system punishes those who like to open stuff, because if you have multiple sets and you have a favorite, the other ones are just completely useless.   It would be nice to at least be able to give them to your alt be able to trade them to somebody who is looking for a specific set.     
 

The best example I can think of is there has been a person in gold looking to buy a purple Ceruledge set for weeks.   I have one I would love to trade him, but instead it’s just sitting there not being used and there’s not enough people getting drops to keep the market healthy with them.        I don’t see any benefit in locking the sets.  They should be tradable just like the mounts.     .

Edited June 29Jun 29 by Rhulk

I like the idea of making the PvP cosmetics tradable, but I do not think they should be like PvE item's "rotated-tradability". Some players want to sell their PvP rewards asap and would not want to wait X amount of months.

Instead, there should be a small fee to make the cosmetic tradeable after opening its contents.

For example, a player wins the cosmetics via PVP chest reward. They open the cosmetic and wear it for a few weeks. Then when they want to make it a tradable item, they can pay a NPC X amount of pokedollars to do so. I am sort of thinking of these as "mega-mounts" which are not tradable unless the player devolves them.