They have a word (the pornography people do) about the hyper-specialized nature of porn, now. The idea is that naked people whipping midgets with leather belts is saturated, too competitive and therefore not cost effective to get into, and get some kind of ROI. "They" say that what a newbie in porn needs to do is to define niche that is so exotic that no one else is uh "servicing" it, meaning that your site would need to be about naked people inside prison cells whipping red-haired midgets with a purple leather belt.
So the problem, as I see it, is how to describe this niche, not only in ways that are accurate, but also in ways that anticipate what your prospective user might be looking for. 1) Exactly what long-tail keywords would you use to describe this unknown and unavailable new porn niche, and 2) How likely are people going to be to use those words to find you.
Note this is an SEO forum, and not a porn-fappers paradise. So the focus here is not on the slowly oozing body fluids and the shrill and ecstatic cries of the leather-bound midget being waterboarded, but rather the words that would be most effectively used to described those images and sounds. It sounds to me that you are attempting to take a personal interest of yours (midget porn) and trying to find a way to take what you like and sell it to others (doing SEO on a midget porn website). While noble (many successful people love what they do and do what they love for a living), the measure of your future financial success isn't going to be about whether or not your micro-niche makes most people at least 3/4 erect (including yourself), but whether or not the financial circumstances are such that there is money to be made. The only people making money with an erection are porn stars, and they need viagra in order to do it.
The biggest flaw I see in your business plan is that you fail to see the difference between selling porn (or anything else) and MAKING porn. You've said it doesn't exist, which implies then that you are going to have to make it. And that's not marketing, that's manufacturing. The guy that sells iPods isn't making them, and the guy that's making them hires someone else to sell them.