You see there is a reason people are fooling you.
Your plans are nice and all, but they just cant work out if you put the current mechanics into consideration.
First of all there are no bridges and it is unlikely they will get added soon.
Second, it is unlikely that we will get the fractal map, thus there will be river system for each grid. Thus you dont need a trading town at all, no one would use it because its too much effort to sail and trade there.
Also you have a not so nice history of not so nice dedication to your "projects", thus it is even unlikely that you will even try to build it, not even speaking about that no one will want to help you. Just drop it and make a normal village with some friends, or join one (and stay there this time).