If two traders both pledge tokens to a smart contract, and the tokens can only be unlocked and returned if both parties agree, then if one of them acts maliciously, it would result in a lose-lose situation, if the transaction is completed smoothly, they'll naturally agree to unlock their pledges.
This way, there's no need for any additional escrow, just communication between the two parties.
Implementing this logic with a smart contract is simple, and the whole process involves only the two traders and the smart contract.