Suppose that the heavy plough was introduced to Europe from China not during the early Middle Ages, but instead a century or two before the birth of Christ. Would this allow for economic growth among the peoples of Germany, Britain and Gaul? If so, would this be an impetus for the formation of larger, centralized states in those regions? What would those states look like? If the Romans achieve supremacy in the Mediterranean as OTL, would they have a harder time subjugating Gaul as a result?
I haven't really put much thought into the idea, it just came to my head at random.