Hi,
I have seen some posts about trading items, the problem is players with powerful items could give them all to an account to make it powerful. This is a solution.
1) Only allow 2 traded items per account, includes both receiving and giving (so if you sent an item, that counts as 1, if the other player gave you another item that is both trades used up for both players).
2) Drain all the fusion from the item.
3) Trading an item costs 2,000 credits for normal items, 5,000 for rare, 10,000 for epic, 15,000 for legendary and 25,000 for mythical.
4) Both accounts have to be within 2 levels of each other to trade.
I think this solution would remove the 'OP' aspect of trading.