At the moment, as far as active quest coders are concerned, we have only Bartolomeu o Portugues.
Short Jack Gold works on the Hornblower storyline, but personal issues have prevented him on continuing that for a while.
Captain Maggee does Jack Sparrow, but he's too busy with school.
For the Standard storyline, nobody ever did any real work on it other than fixing and adding/adjusting sidequests.
It's the stock game storyline, so we never needed to do much with it.
We did intend to remove the film influences from it altogether and leave the Jack Sparrow-ish affairs to his storyline only.
There's also been thoughts on expanding the storyline, adding stuff inbetween as well as at the end, but nobody ever started work on that.
Since you've expressed interest in doing storyline work, why don't you start out on adjusting the Standard storyline first?
Starting out with your own will be tricky at best, while adjusting the existing storyline will help you understand how things work.
You can start out with removing the film influences, which will only require some character and ship model changes, as well as dialog adjustments.
Those are very easy to do. Then you can try to rewrite the story a bit to make more sense as a stand-alone story.
And if you've got any thoughts on how certain scenes inbetween could run a bit more fluid or interesting,
you can start quest coding in adjusting those. Then eventually you would be able to expand it to such an extent,
that even for players familiar with the original game, it'll still be worthwhile to replay it.