Old daemon and wallet version 0.18.3
Joint Trading Wallets
The world needs a locked trading wallet, where two traders agree on a trade, and then both put their coins into a locked joint wallet, and then each trader must unlock the joint wallet to complete the trade, and the commissions are 0% Unfortunately I have zero skills in that department
What you describe sounds like a multisig wallet to me.
Bassically it is a wallet address, where coins can sent to (= both traders put their coins in ).
When coins are to be spend both (or 2 of 3 ) parties must sign the transaction before it is sent to the block chain.
This feature is already implemented.