Probably not. Dutch ideas seem pretty superior to any of the minors (presuming you're going to go naval), and they get extra missions. I just started a game as Flanders but for some reason I don't really want to form the Netherlands, but I feel like I'd be missing out if I don't. I just think the idea of an alternative Flemish formable (some form of Belgium maybe?) would be pretty cool. Maybe I just like the world Flemish. But Flemish England has a nicer ring to it than Dutch England. 
Is there any argument for having Belgium in the game?
Is there any argument for having Belgium in the game?