First of all, the game feels really good, even if it's still in very early stages.
My suggestions:
Switches for easier navigation in the battles.
Speed: [stop], [cruising speed], [full speed ahead]
Rudder: [hard starboard], [hard port] , [straight ahead]
Ship designer:
Switch [+] [-] for speed and other values. This is easier to use for small changes than the pure slider.
Switch to optimize the speed and / or other values. It often happens that the remaining tonnage should contribute as much as possible to increasing the speed. There would be a good way to automate this.
Fleet overview:
Filter to show only certain ship classes as "only BB", only "CA"....