I am not suggesting anything of value just an ability to target the enemy that bit more accurately at larger ranges when you have to aim above the masts by more than the height of the mast to get a hit. And an Elevation reading would not be as easy as you think, you would still have to fire a ranging shot in order for it to mean anything and even then there is no guarantee that you get it right second shot. The enemy can still take evasive action after the shot as i often do changing your heading by as much as 2 degrees can throw enemy off, the Elevation i am suggesting would simply be so you know what the angle your guns are set at is.
Historically the captain would not worry about such things as others would deal with it, however as we are sailing the ship and manning the guns a reading for the angle could speed up the process of ranging and shoot at the target. It could also mean less collisions between friendly ships as you have more time looking around to see the battle develop. It could allow for more fluent and dynamic battles and still retain a element of skill, a skilled player will be able to judge the roll of the ship and still have his runs set to a certain height. Instead of the current trying to keep you mouse still inbetween the roll of the wave trying to guage the range of the shot adjusting the range firing again, all the time while trying to avoid hitting other ships.
To much work load on the individual captains would make the game much harder to play for some of the more casual gamers, this would in turn effect how many people play the game. Its a hard balance but go too hard and players will be limited to hardcore gamers harming sales and the future of the game, to easy and people get bored. The only option that makes sense is to meet in the middle as i cannot see the games developer wanting to make a arcade mode and a realistic mode. And besides the more people that play the game the more ships you get to sink and more the developers would add new things in due to having more resources available. Just food for thought..