'Nother story idea. NC, possible extreme elements, very much up for discussion. It also involves throwing plausible science pretty much out of the window!
'Side effects may vay'
This story revolves around a failed drugs test - or at least, one failed drugs test. The drug in question has reached human testing trials, and has been designed to dampen down testosterone and haemoglobin levels. It's thought that if it works, it could be used to deal with violent and/ or erratic behaviour in prisons and mental homes. The tests begin, and a group of young male volunteers take the drug and the effects monitored.
All goes well, with all men showing decreased levels of testosterone and haemoglobin - apart from one case, your character. In this case there are boosted levels of all sorts of hormones - including estrogen. One of the scientists in charge, my character, is tasked with determining what is going on in this subject. A few tests show that a whole variety of different cellular compounds are being up and downregulated in shockingly drastic ways - in this test subject, the drug is actually transforming him into a woman. To compound matters for the subject, skin tone and other features are being mutated, slowly pushing him to become not only a woman, but a black woman - totally destroying his old identity, if the changes are allowed to occur.
An inhibitor is known about, and a more caring scientist would deliver it promptly - only, the scientist being charged with his case is less than caring. He's an embittered divorcée, and perhaps that bit unhinged by the stressful breakup he had to endure months ago. Suddenly he has a very tempting prospect on his hands. Not only does he have a very interesting case study to observe, but if everything proceeds, he also had a new 'woman' to toy with. And by the end of the transformation, he - or rather, she - will be indistinguishable from any other young black female. And for your character, the poor test subject, the scientist has a potential drug to reverse everything - why wouldn't he start to do as the good scientist says?
The story will revolve about the man's transformation into a member of the opposite sex, and transformation into another race completely, whilst trying to decide how to react to what the scientist is asking of him. Will he obey? Will he try to resist even as everything is going on? Do PM me and we can discuss more deeply.
The requirements of my partner that I ask for:
*I enjoy nicely detailed posts. I'm only looking to play this game with one person, since I have a few other roleplays ongoing. If you're comfortable with shorter, faster games I'm not particularly likely to be your perfect partner!
*Your interests should ideally include heavy use of bondage & restraint (towards the latter part of the story), mind-fuckery, anal and oral. There are several other kinks I had in mind, but these are the predominate ones. My two hard limits (ones I'll never play) are scat and bestiality. All else works well.
*Obviously anyone can pick up this role, so long as you can play both sexes well!
*Finally, I ask that you play the role somewhat realistically whilst allowing the story to flow nicely. Of course, the concept is a very odd one, which is why I'd like to discuss more in PM if you're intersted.
Whilst I am only looking for one partner,
this is not a first come-first serve deal, so
please don't feel you have to rush to get my attention! 
Have a think about the role if you're interested, and contact me at your leisure so that we may discuss everything in much more depth.