In trades where multiple (at least two) parties can execute proposed offer, second (slower) player should be able to +1/improve offer upon initial offer accept of first player (e.g. +5-10 second window).
For example, player A proposed rock for wheat. Player B accepts first. Player C can also execute same trade.
Player C has option (e.g. ~10 second window) to offer better proposal - e.g. +1 any resource.
Unlike most popular feature request, I disagree that player trading should be able to choose between first and second player with same offer. Second player should be tracing game better, and be faster.