For genderswitch, here are two slow transformation Dean stories (including sort of dark Sam) off the kink meme: Improving Nature (http://spnkink-meme.livejournal.com/33949.html?thread=8075933#t8075933) - Sam is obsessed with the idea of making Dean a girl Girly Girl (http://spnkink-meme.livejournal.com/4278.html?thread=2228918#t2228918) - Sam gets Dean on steroids so he becomes very feminine
Also, I haven't read this one, but I think it fills your first request: Big Brother Omega (http://spnkink-meme.livejournal.com/68645.html?thread=22322725&#t22322725) - Omegas aren't born that way. They're made. Every child born to an Alpha/Omega parents is born Alpha. Daily exposure to the hormones present in Alpha semen turns an Alpha into an Omega.
no subject
Improving Nature (http://spnkink-meme.livejournal.com/33949.html?thread=8075933#t8075933) - Sam is obsessed with the idea of making Dean a girl
Girly Girl (http://spnkink-meme.livejournal.com/4278.html?thread=2228918#t2228918) - Sam gets Dean on steroids so he becomes very feminine
Also, I haven't read this one, but I think it fills your first request:
Big Brother Omega (http://spnkink-meme.livejournal.com/68645.html?thread=22322725&#t22322725) - Omegas aren't born that way. They're made. Every child born to an Alpha/Omega parents is born Alpha. Daily exposure to the hormones present in Alpha semen turns an Alpha into an Omega.