The game is unplayable due to the wares flow problem. As stated the newest warehouse is the target for wares flow (from and to). If built, wares from other warehouses are transported to the newest one. The flow of products quickly creates a traffic jam to the warehouse and from other warehouses. The products being moved create jams that makes flow of products currently produced impossible.
I ma using this version:
Widelands-Build14-WinXP-and-newer.exe WinXP and newer Windows 66.5 MB 2009-09-27
Here is an illustration: http://yfrog.com/htflowproblemp
You can see an empty headquarters and a clogged warehouse from which goods are being transported to the newest warehouse. The headquarters isn't being used by settlers anymore.
The game is all about economy, without efficient distribution infrastructure, the game doesn't make any sense :/
Furthermore, it would be great If a product could be transported by a longer route. Mayby creating an algorithm that would take into consideration predicted length of transportation based on jams would be too hard to create, but for example a simple 20% margin given the best route ? Or an algorithm based on Q-learning or an Ant algorithm, that could work.