Why not fuck... yourself?

You look at the two sexdolls and the Zoebot, thinking about the possible fun you could have with them. Then, a passing thought strikes your fancy. As you are now effectively in Zoe's body (with your head and your fathers dick), why not put your sister in your own.

You zap her again to the sexdoll form and swap a few parts here and there. Another zap and...

"What the?" Zoe asks as she wakes once again as a human and feels her body. Well, she has a reason to be surprised. You have found that the breasts are another detachable feature on the sexdolls. Now your sister is in your body - or rather her head is attached to your body. But your body has your mother's tits and pussy. Taken in full, your sister looks like a woman, maybe not the cutest one, but a woman nonetheless.

You on the other hand are pretty much a shemale, with a raging dick ready to fuck that pussy.

And there are some random detached sexdolls parts around, but whatever...