I disagree here. It still shocks me, but an awful lot of sailors in "ye olden dayes" never did learn to swim. The one explanation I heard didn't make sense, really, but everything I've heard confirms that it was so. So, I don't think that the water-worthiness of gear would be a big consideration, if we're looking for "historical accuracy". Which of course doesn't apply in Oblivion, where none of Earth's technological development paths was followed.
Shockingly, I've also heard these stories but I never believed them to be true. I mean, come on, pirates and sailors that can't swim? Silly, right, but that's what I heard.
Kafana, I don't know if you're still looking for quest ideas, but what about a chance to save an attractive person of your gender-of-choice? A good, swashbuckling, roguish rescue story never goes awry, in my opinion. This could perhaps be part of the buildup to the confrontation with rival pirates; your lady/gentleman was kidnapped by those awful beasts! Go pick a fight that will inevitably lead to retaliation!
This is an extremely interesting idea, one I just might work on. Thanks for the suggestion.
There could also be a side quest to find treasures left behind by a legendary pirate of yore. These might be in one central location, or scattered here and there; they might be stumbled-upon if you thoroughly explore quest locations, or found after following a series of clues.
Something similar is already in the works but thanks for the suggestion

Also, somebody mentioned getting stranded on an island. I think that there are a lot of possibilities there, depending on how elaborate a setup you were willing to make. The player could have a variety of goals to accomplish in order to survive and attract rescue; the island itself could have secrets.
I've thought about it, but it's not really a priority at the moment. Once I do finish this mod (at least most of it) I'll probably add a small plug in that will allow and alternate start, one which will offer a lot of roleplaying value to the player.
Good luck with your mod,
Asterai
Thanks for the support and suggestions

Cheers.