Some story sketches:
Mafia boss with bimbo fetish, if MC raises femininity to certain level, one of guards approaches him and tells he's working on somebody, looking for those who are not afraid to grow extra assets. MC led in big luxurious cell where he meets mafia boss surrounded by stunning huge-titted bimbos, who offers MC in very friendly way to become one of his bimbo babes.
Rules are simple: blonde hairs, high heels, light-hearted personality and pornstar body. It can has quest stages of MC reaching certain body sizes and getting rewarded for it, newborn bimbo in beginning, then certified bimbo and then ultimate bimbo if MC grows tits, ass and lips bigger then all boss's girls.
Trans prison warden with a crush for MC, who wants to condition him into personal cumdump addicted to hands-free painal orgasms, giving him hormones and putting numbing cream on his dick to get MC used not to touch it during their rough anal sessions. She notices MC if he gets his ass grown too juicy, and wants it even bigger to slap while she destroying his asspussy.
Ideas for masculine MC:
Mafia boss who is transsexual himself. Younger son of mafia family who wanted to feminize himself before getting into jail, took the blame in court for family crimes when they asked and got in prison for a long time. In prison he decided to achieve his dream and after years turned into influential prison matriarch with help of money and power of family which wanted to get rid of him.
If MC is masculine and strong he can be chosen to become her fuckboy, with boss dominantly riding his dick with her ass. It can turn into romance, if MC will be affectionate and uncover softer side of his lover.
First feminized inmate, in prison gym MC meets beautiful mature woman with multiple tattoos who works as trainer for higher-up prisoners, he discovers that she was the first who was forced into hormonal drugs to become prison slut 20 years ago. If MC will raise relations with her and become her friend, she will ask him to help with her problem and keep it a secret.
She tells that after many years of brutal anal she got dependent on it and can't cum anymore, her dick is permanently soft more then 10 years and anal masturbation can't satisfy her no matter how hard she's fucking herself. She explains that after earning escape from being a slut and becoming a trainer she didn't had sex for years, and asks MC to fuck her ass violently and without any mercy.
Here MC will have two choices, turn her into secret personal bitch addicted to rough anal, or refuse and start regularly have tender careful sex with her despite her disappointment, until she finally orgasms from it with tears of happiness in her eyes.