We have all seen, on many occasions, the chaos that adding a second gunner to a ship can add. It causes the engineer to throw things, the pilot to scream obscenities and sibling rivalry among the other gunner. The tactical benefits are almost non-existent however. I believe that the argument of three gunners on a ship should be just as valid as the argument for three engineers, or any other combo of the two. In short, this would be accomplished by adding in passive bonuses to the gunner to allow them to better work their magic. A ship with three gunners on it, as an example, would then be viewed as a very dangerous glass cannon as opposed to a very laughable glass target. Guns of Icarus has all the makings of a strong competitive game. The mechanics are simple and the strategies are complex. Every individual can bring their own play style into the fray and it will often be reflected in very unique ways in the game itself. Adding in passive bonuses to the gunner will only compliment those qualities while also making the game more accessible to a wider variety of players, namely those who wish to play as a gunner on a ship. This change would also continue to increase the diversity among teams which can only lead to a higher quality of competitive play.
The passive changes to gunner would have to be addressed by Muse, however I believe that non damage buffs would be appropriate. Faster reloads and increased turning speed are a few options that could always be tweaked later as needed.
I'm sure this isn't the first time this has been discussed, though as the game continues to grow the discussion should continue to grow along with it. Your thoughts are more than welcome.