True; it would be more difficult to build there. Many of the mills I am familiar with used a man-made dam to form a mill pond and direct the full stream over or under the mill wheel, thereby maximizing the power available to the mill. But then, the number of medieval mills I am familiar with is vanishingly small! Most of what I know was gleaned as I researched for a map of my own a few months ago.
For a mill placed there, I'd probably narrow the channel to force more of the water to move under the wheel. Stone retaining walls on each bank to channel the water, and then put the bridge over that, since it can share its footings with the walls and also be much shorter.
As it stands, though, it is a fine-looking map. I'd like to see some labels telling us what some of the buildings are, though.