...He thought about it, deciding on none other than the place babies come from, the womb. It's already designed as a tight place for humans to stay in, albeit only until birth.
He selected it, and decided on an extra edit to the instructions to fit this. "Even when containing others, it's possible to become pregnant. The pregnancy is mostly the same as a regular one, however, depending on which side someone is on during this, they may end up stuck inside. Others can still enter and exit a pregnant womb as long as they aren't behind the fetus. It's also possible to impregnate a woman from inside."
"When the host is pregnant, it's possible to enter the amniotic sac with the child; However, it's not possible to exit the sac all the way until child birth. This would be entirely habitable, and it's possible to go into the child; Doing so is dangerous until the gender is decided, however. If someone is inside the unborn child as the gender forms, and it develops into a boy, they could end up completely stuck inside."
Jeff sees this as perfect, and he decides to confirm this change. The chronivac does it's thing...