This meant adding a third type of crew member, Air Grenadiers, who are elite troops with fancy hats. Instead of jumping across, these would throw grappling hooks at enemy ships and then launch themselves across. In practical terms, this meant changing parts of the boarding process for them: they would still exit and enter ships in the same way, but the process of moving between ships would be different.
Once on the outside of their ship, instead of finding a suitable place to jump from, they would instead find a spot where they could fire a grappling hook at the enemy ship. The hooks obviously have limited range, so while grappling is a lot safer, and has more range than jumping, the two ships still need to be reasonably close.
Having moved to a suitable launching spot, they fire the hook and wait. If it fails to hit, they move if necessary and try again. If it does connect with the enemy ship, they let go of their ship. At this point some basic rope physics kick in, constraining their fall into a graceful arc, as they winch themselves towards the ship, shortening the rope over time.
Eventually, they make contact with their target ship, and everything proceeds as before.
Having built the grappling hook feature, there were still a lot of things to do for the next version: I created AI for positioning ships for boarding, added some basic animation for crew and weapons, fixed a whole bunch of bugs, and so on. Right now, I'm putting in some time balancing and polishing the single-player strategic mode, but I expect you'll be able to play with these new toys soon.