
breithauptclan |

The item looks like a GM Prop for allowing retraining a character's ancestry - which normally can't be retrained.
I have to assume that the character's player and the GM are already on the same page regarding which ancestry the character is changing to. As such, I don't see any balance reason to forbid Automaton or poppet or whatever else as one of the options.
Now, how that makes narrative sense is an exercise in creative writing...

Perpdepog |
It should also be noted that the item does specify that a bit of a humanoid is what makes up the target ancestry and heritage for the potion, and automatons do not have the Humanoid trait, so if you were looking at RAW I don't believe you could use a rebirth potion to transform into an automaton.
Like briethauptclan said though, if this item is in the campaign then there is already some back and forth between a player and GM viz ancestry swapping, so it's not like it'd be a difficult thing to bring up.

breithauptclan |

It should also be noted that the item does specify that a bit of a humanoid is what makes up the target ancestry and heritage for the potion, and automatons do not have the Humanoid trait,
I hadn't noticed that. Though I agree with the assessment that the use of Humanoid trait isn't what should be relied on to allow or prevent using the potion or what ancestries it allows.
What I do find a bit odd is that Automaton and Conrasu would be prevented by the Humanoid trait, but Poppet would not.