I have requested this before, but now seems like a good time to do so. I would very much enjoy it if the ability to change the designs of turrets was added. At the moment if you build a BB for Britain in 1940 you have access to old looking 16" guns, and this makes making the Lion-class, at least visually, impossible. If you decided to make Vanguard the guns are locked in a state that is too modern. However simply changing the gun visuals would be a bad idea, since then choice would be removed (in the 16" case Nelson would be impossible). The 14" guns are also an issue, since the turrets are too wide for KGV. In my now extensive rant I must also include the 6" (British).
This is also probably an issue for other nations, but I frankly know more about The Royal Navy. My "rant" is also not intended as a complaint, I would just like to aid the development of the game, because I really enjoy playing it.