Specualtion ahead
I suspect it wouldn't work because of how movement in the game is programmed, all player movement is anchored to their own ship as a reference point, and adding in an additional ship would be a ton of effort to calculate the additional reference and work out how it influences movement and transitioning from one ship to the other.
It would be a ton of effort, complete re-write of movement system, and would only make it more banal. Cmon guys if you want to whack dudes in the face there are other games like chivalry. What makes goio unique is flying in airships and shooting mounted guns, boarding wouldnt do anything other games don't.