Thanks, great map
Some detail questions (from local knowledge)
What's the naming convention? Brugge and Ghent don't seem to follow the same one?
For Bruges: shouldn't it include the western part of today's zeeuws Vlaanderen (location Hulst), which included its port access for most of the game period? I'd also make it swamp.
On the other side of Flanders: Maasmechelen is a 20th century name. Since there's already a Mechelen, maybe name it Tongeren, which is a Roman town in that location?
Zeeland only one location, with the much smaller (even if complete) Zeeuws Vlaanderen separate seems quite unequal, I'd either not have zeeuws Vlaanderen (adding the remainder to sint niklaas) or walcheren (the main island of Zeeland) separate from the rest of the county. With the size of next-door Breda, probably first?
I also don't like the culture map