Refit Displacement Question

[Suribachi]

Something that has always bothered me is that the displacement of the ship cannot be changed during a refit.  The reason this bothers me is that there are multiple loading screen history lessons that state that the displacement of the ship was increased during a refit.  As an example, this one is a direct quote from the game for the Iowa:

START QUOTE
The Iowa-class represents the culmination of US battleship construction.  Six ships were ordered in 1939 as a response to Japan's noncompliance with the international naval treaties.  Four ships were completed: Iowa, New Jersey, Missouri, and Wisconsin under the 2nd London Naval Treaty which accepted an increased displacement of 45,700 tons.  During World War II they were refitted to exceed 58,000 tons.  Armed with three triple 16-inch guns, powerful AA guns and a top speed of 35 knots, they were unmatched by most warships of their time.  
END QUOTE

What I recommend is that refit allow the player to change the displacement of the ship within the same size as when it was made.  What I mean by this is that when a ship is made, there are certain points when the hull jumps between different sizes.  As an example, the USA Battleship I hull from 1890 is at its smallest size from 11,000 tons to 13,499 tons.  When the displacement is changed to between 13,500 tons and 14,749 tons the hull becomes it's second size.  For the purposes of this example, I will call this medium.  From 14,750 tons up to 16,000 tons the hull is at its maximum size.  During this example, the beam and draught of the initial design are left at 0%.

My suggestion is this:  knowing the information from the example above, if I initially design a USA Battleship I ship to be 15,000 tons maximum displacement, I should be able to freely change that to any number between 14,750 and 16,000 since the hull's shape does not change during a refit.  Additionally, beam and draught should not be able to be changed during a refit since that would change the shape of the hull.