A Small Analysis on the Puzzle Scene:
John: I put together so much of the ground
Michaela: And I completed the sky.
Because John is grounded. He is stoic and calm and was what Francesca needed- a solid foundation to support her. Someone whose personality matched hers and who gave her comfort but also belonging- in society and in her own family, both places where she has never felt the same as everyone else. Marrying John allowed her to take her place in society whilst also giving Francesca someone who simply understood her.
Michaela is not this. She is as Francesca describes- chaotic. She does not want to get married, does not want to adapt to societies expectations- so she does not. As much as she can be as a (queer) woman in the 1800s, Michaela is much like the sky itself- open and free, quite the opposite of grounded.
And as Michaela herself says in this scene: "You cannot have one without the other."
Both the ground and the sky are needed for life to exist- both John and Michaela place the last piece of the puzzle together, and both are needed for Francesca's story to play out in full. A story that yes, is about fertility struggles, but is also about her handling her grief and dealing with the guilt of falling in love with her late husbands cousin.
Francesca's feelings of guilt and shame will not only be about who Michaela was in relation to John, but now will also be about who Francesca is herself. Something that I feel can only be enhanced by Michael becoming Michaela, not hindered.