IF YOU MAKE THE CASH SHOP COSMETIC ITEMS TRADE ABLE THE GAME WILL BE PAY 2 WIN.
If you allow the cosmetic costumes or mounts to be traded this is what will happen. People that have a lot of money in real life will have an advantage. They can buy a costume for real money and SELL THE COSTUME FOR IN GAME GOLD TO OTHER PLAYERS!!! THAT IS A BIG NONO. If this is allowed than you will have people using their real life to gain advantages. The game will turn out just like archeage. DO NOT BE GREEDY custardS! IF YOU ARE GOING TO SELL COSMETIC DO IT LIKE PATH OF EXILE OR LIKE WORLD OF WARCRAFT, NOT LIKE ARCHEAGE BECAUSE EVERYONE WILL LEAVE AFTER 1 MONTH. Please I am begging you, do not allow the cosmetic items to be traded and no RNG boxes with traceable loot either.
EDIT FROM Dredja: Make cash shop items account bound or player bound to prevent trading.