If you are still needing ideas, here's a few I'm spreading around.
1. A female explorer stumbles upon an ancient tomb, and awakens a Futanari Queen who's cum contains a potent aphrodisiac and hypnotic effects, the more one consumes the more the queen controls them. Now freed from centuries of sleep, the queen seeks to make the explorer her sex slave and forces her to suck her off.
2. A woman has gone to prison for a crime she did not commit, and will likely remain in prison for the full sentence by the time investigators discover the truth. Her cell mate is an extra-rapey woman who is looking for a new prison bitch, needless to say the new comer cannot put up much of a fight, and eventually learns to accept her fate as she is being raped.
3. Two princesses from different countries at war with another, a human and an elf, are in love with each other. but because their nations hate each other, they know they can never be together. One is to be arranged to marry a man she has hated her whole life, and the other already has suiters looking to court her as well. So the two of them sneak off to a forest between their two kingdoms to have sex one last time, but this time theres a bit of a twist. The elf has brought a magic potion that would allow her to grow a penis and impregnate her lover, she figures that if she's going to be forced to marry a man she doesn't love then she refuses to have her first born share blood with a man. The human feels the same, and agrees to the elves idea. (this one would require position changing, but if it's too much for you then just a BJ is okay too.)
Yuri and Futa/Girl dialogues are in very short supply on this side of the forum, or at least that's what I've noticed.