I kind of see where both sides of the argument are coming from.....fighting breaking out on deck would severely detract from the actual ship combat, especially when people in online games seem to have a CoD mentality about everything.
That said, if it is already possible to jump on someone else's ship, I wouldn't mind there at least being some kind of recognition for doing it.
I've already seen that most ships tend to have 1 Pilot, 1 Gunner, and usually 2 Engineers, but there have been multiple occasions where all the Gunner is really doing is just standing on the same gun at the front & firing their better ammo - it's situational, but I could see how a third Engineer could replace a Gunner depending on what's happening & what ship you are piloting due to the game's current setup.
I don't think adding an extra crew slot/role to allow for specialised Saboteurs would help maintain game balance......though alternatively, giving the Gunner an extra tool he/she could opt to use that would let them tie a rope to one of their gun posts, jump to the nearby enemy ship, plant an explosive of some type on deck, and then finally yell out to be pulled in by his/her crew (crew still on the ship would simply tap the gun that the Gunner was tied to in order to reel them in) sounds as if it could potentially be worked in & still maintain game balance & teamwork. The ship at risk from the explosive would simply need to spot the Gunner & their tether & whack it with a wrench or something to send the Gunner flying off the ship - an activity the entire crew can be responsible for, especially since combat is usually hectic enough that it may be harder to notice an enemy Gunner dropping out of the sky.
Obviously, using this maneuver would mean your ship is taking a risk to get close & use up a Gunner & ammo/item that you could have loaded into your guns - especially risky if the game is set so that the jumping Gunner would have a NASTY respawn timer to deal with if their safety tether is in any way cut before they return to their original ship. Ultimately, if the Gunner were to successfully plant a bomb but have their rope yanked/cut to send them flying overboard, the Gunner's only option at that point is to wait out the respawn time.....if the bomb does enough damage to take out the enemy's hull, the ship blows up & resets, but the Gunner is still gone long enough to make it a penalty for failure.
Even if that wouldn't work well in Ship vs Ship combat, the idea could still stand for Adventure Mode if you're jumping onto another ship with the intent to steal item crates along trade routes - no hand to hand combat, but simply needing to look out for that rope to cut.
