edit: did not see snk's post about making a trade table before posting this, if for some reason Stefan says no to the trade table this would be ideal, otherwise if he says it's ok this idea is 100% pointless
So according to stefan, there will not be a trading system. However, you can drop items and people will attempt to trade with this, however it results in tons of scamming.
What needs to be done is some creative form of drop exchange that is not exploitable that allowed people to trade
Droppable items only
It can be anything really, like a " 1v1 minigame" where each player puts items on a box, with each player able to see the other's items placed, and eventually press "ready" to start the game. When it starts, each player is placed in a seperate level with the items spread out across the level. it's a race to see who can pick up who's items faster, and you get a chance to pick up everything. Winner get's absolutely nothing except to brag that they won. The key is that it's a safe method of trading items disguised as a minigame lol.