This is something seen all the time in swashbuckler movies.
It just looks cool. I doubt it is terribly realistic, especially swinging from yards or a crow's nest to the main deck. I imagine that most attempts to try it ended
badly. However, since our inspiration is films and not reality, this is definitely something that should be allowed.
So, the question becomes, "what is the purpose of swinging on a rope in pirate movies?" Generally, the answer is, "to get somewhere fast." The reason to get there fast may be different, but no matter what the reason is, you don't see it used a lot. So, my proposal is a universal stunt that all named characters have that is something along the lines of:
Once per scene when you are on the main level or above, you can instantly find a rope that will swing you to any other zone on the main level or above.