With plenty of rivers around, why not utilize them?
For example, building a lumbermill in the same vain as the windmills. Store a bunch of trees and they'll be turned into planks on mass. Naturally a building like that would be quite expensive to make, requiring you to be your own lumbermill for a time being. In addition, you could build your own bridges and the lenght of the bridge would determine how expensive it would be to make, (i.e 1 square of lenght will cost 30 stone and 10 dry boards or something)
Aswell, how about the idea of being able to connect rivers together? I'm sure some of you've walked past a lake with a river not too far away, wondering why it isn't connected. Canals need to be dug out (obviously) and a sandbag barrier needs to be constructed to hold off the current until the canal has been finished to the pilgrim's desire. Then the sandbags would need to be blown up, or the pilgrim could risk opening the canal by hand and risk getting swept away by the current.