I've read all the comments so far... and I agree with most of them. However, I don't think you're going to accomplish much with a BBS. Ok, your time is limited and this is what you've got, but seriously, you might want to consider a MySQL backend with at least a php front end. That way you'll have much more flexibility with how you handle this issue.
I do run a MySQL backend with a PHP front end. And without being a PHP/HTML guru of sorts, I do what I can.
If I were at work, I would say that this is a prime example of bending an app to serve needs that were never meant to be met at design time. In my opinion, you either stick with what you've got or swtich platforms.
To...what, exactly? If you have a particular recommendation that can handle the traffic load and import my existing db that costs less than about $200-$300, then please let me know. I've not found anything at all. I've purchased Expression Engine for another portion of the site; I've purchased SubDreamer to lay over the existing forums, but there is nothing that will magically do whatever it is that will protect this site (?). Short of starting from scratch and programming a php interface like FFN, I have no idea what I can possibly "switch to", and I think anyone who knows something about dbs and php programming would know that would take someone who has a full time job already several years to create and perfect. And even then, look at FFN - they ditched the adult-rated content. So, I'm not sure what it is you're suggesting here.
It's not going to protect curious eyes and you don't have that responsibility as others have said. You need to evaluate what your goals are in hosting this site and specifically what you want the users to be able to do.
Originally, my goal was to provide Heero x Relena fanfiction on as close to an up-to-the-minute basis as I could get. Because that was why I came to this site when I first entered fandom - Zoe updated every day or every other day. And when she was going to shut down the site, I (as well as several others) begged her to let us have it, and she did. But I was a terrible webmaster, comparitively. I'm a writer, not a web guru. My heart was in the right place, and I've learned whatever was necessary in order to create what we have now.
What is my goal, now? To provide a "safe haven" community for anime fans of het pairings - the ones who get tired of having to argue every other minute with someone on the more "open" fansites about why they like such and such het pairing or character. To provide a more 'family' (as in a community) type atmosphere as well as a place where people can feel welcome to post their stories and artwork.
Me, personally, I can't post all my stuff on FFN because of the adult content ban. I can't post all my work on Aishiteru because some of it is for other animes. So, I've got this contingent of work posted on this website, I've got that set of stuff I can post to the other website.... So, yes, it's important to me to be able to keep the adult content because it's generally very rare to be able to know that every story you click on is not going to be this inordinate SURPRISE as to what kind of content you might find. I've stumbled upon het lemons where the man was thinking of...another man in the midst of having sex with this girl, and that was not marked on the story. But I would have at least liked to know that would be in there before I clicked on the link.
So, it seems like, we have that extreme in fandom (surprise, there's a yaoi lemon in here) or the other extreme of "No adult material whatsoever (but still be careful because you may accidentally find Heero lip-locked with Duo)" and Blissful was about providing het romances of all ratings.
Does that answer your questions?