Trade system

Widelands need a trade system.

My proposal is that every player that wants to trade must build one or more "Trade Center" or "Market". This building need a "Trader" (carrier + donkey) to work. At markets, player must select an amount of one good to trade (export), and what goods want in change (import). When goods to export arrives to market, then trader get goods and start to walk towards discovered Markets. Trader can only walk to any discovered market on map.
When trader arrives to a other tribe market that tribe can select to accept or reject trade. If trade is accepted, then goods transported by trader are deposited on tribe market, and trader get exchanged goods to get back to his own market. Market goods are picked up by carriers and then added to player economy.
The more markets, more traders to travel arround.
Every trader can transport only up to 10 goods at time, but should move slower that normal carrier, maybe 1/2 speed?
For human players, when a Trader arrives to one of his markets, a visual icon of trader should be shown, and when player clicks on it a dialog of trade is showed with two buttons: Accept or Reject.