For me it look like the benifint from naval buildings are rather weak.
If you discount the local ship repair and build speed as rather irrelevant bonuses, a province with the 4 basic Naval buildings will have 0.33 trade power, 10% cost discount and +1 force limit modifier compared to the 4 basic buildings in the other building groups, this feels rather weak.
If you discount the local ship repair and build speed as rather irrelevant bonuses, a province with the 4 basic Naval buildings will have 0.33 trade power, 10% cost discount and +1 force limit modifier compared to the 4 basic buildings in the other building groups, this feels rather weak.