Moustache-raygun, growing moustaches on enemies.
Seriously, boarding action just breaks the game spirit. Crewmen doesn't die form heavy airship fire, why do you think you can kill them with a revolver?
But, do you know what do you can do? Throw them overboard.
*Daydream mode: on*
I'd love to se boarding weapons to push enemies (left click), and avoid being pushed (right click). Kinda - Revolver: Push *****, Parry *; Cutlass: Push ***, Parry ***; Rapier: Push *, Parry *****, etc... To make a kinda swashbuckling duel, helping mates being pushed and teaming up to push certain enemy...
Those who fall respawn normally unless an enemy captain takes the helm of your ship. Then its colour changes and fell over crewmen just wait like when the ship is destroyed until your captain is pushed overboard and respawn a new ship, or he just takes the enemy off the helm.
That could create a new class, the boarder/soldier/whatever, and a new kind of maps, capture ships (and flying them back to base for points) / protect the vip.
*daydream mode: off*