That could cause inconsistensies with the spots where the corners of two blue squares touch.
I'd rather that we don't use predefined mapping areas at all, but instead allow plots to be requested in more of a freeform manner. Perhaps we could use a very dense grid that divides the world into lots of tiny squares? Or maybe a hex grid? That way someone who wants to map a particular geographic area could request a plot made up of the relevant small squares/hexes. To prevent anyone hogging up too much space or otherwise causing problems we could state some simple rules such as "a claimed plot may only include up to so-and-so many tiles" and "all the tiles of the claimed plot must be contiguous". And if we want to have buffer zones between maps to prevent inconsistensies arising on their borders, we could disallow claiming tiles that directly neighbour already claimed areas.