Two suggestions for maneuverability realism related perks or consumables:
Ability to perform a 'barn door' crash stop on certain BBs, and maybe larger CAs. Historically, some twin rudder BBs - certainly US ones - could manually set the rudders to sit at 90 degrees, adding a ton of drag. Interesting account of this here: http://www.navweaps.com/index_tech/tech-054.php. Being able to do this two or three times (though at the expense of another consumable) could be kinda cool.
Some sort of maneuverability expert skill might be cool, based on the premise of independent engine control / asymmetrical thrust on ships with two or more propellers. With this active (again maybe best as a consumable?) you'd able to decrease ship's turning circle and/or do advanced maneuvers like slowly turning on the spot (think how useful this would be in a DD). Historically accurate and although actual naval combat wouldn't have called for it very often other than in dodging torpedoes etc, the big historical example of this is Bismarck, which like all German BBs had triple screws which were too close together at the stern to allow her to steer effectively with the props only. Which meant she was stuffed when her rudders were jammed. But most WW2 naval vessels could pull harder turns by stopping or reversing the props on one side at the expense of losing speed in the turn.
