So, I don't think I've seen any Jacob/Queenie headcanons of yours yet. How do you think their story will play out?
Well, we know that Queenie went to visit Jacob in March/April of the year following the events of Fantastic Beasts and that it appears he had parts of his memory intact.
I think Queenie and Jacob are likely to use this meeting as a launching off point to embark on a relationship. She may possibly quit her job at MACUSA to work with him–he does have a Help Wanted sign in his window when she visits, after all.
I can’t actually see Tina putting up much more than a token protest at this, despite her position as an Auror. Tina was obviously and visibly heartbroken with having to say goodbye to Jacob, as much as Newt and Queenie–so I think her only wish is for her sister to be happy. That said, I also think Tina, being the pragmatic soul that she is, will likely start secreting money away to ensure that Jacob and Queenie can make haste out of American should the need arise.
Invariably, the need does arise, though not through anything as drastic as being caught (my sense is that MACUSA is incredibly understaffed for the sheer amount of volume they have to manage and that they are inept to the extreme.) Jacob wants to marry his Queenie, and he cannot do that in America. Queenie is only too happy to have him, so she agrees–and he being the successful business owner that he is, he can sell the bakery for a tidy sum and immigrate to England, France or wherever they choose (I’m thinking France.)
This coincides nicely with the changes in Tina’s life, revolving around a certain British magizoologist who wants her for his own, but cannot legally have his creatures in America…
Jacob sets up another bakery in France, and shortly after, Queenie Goldstein becomes Queenie Kowalski. She and Jacob start a family right away, more due to the lack of contraception during this time than anything else (they really, really can’t keep their hands off of each other.)
Queenie basks in her new role, and when Newt and Tina wed and come up against the kids-vs-career issue, Auntie Queenie is more than happy to provide childcare for their son (Newt and Tina only have the one, mostly due to secondary infertility issues) since Jacob is prosperous enough to hire help in the bakery.
She gives Jacob a large family of their own in the meantime, and the four of them prove a loving, cohesive family and support system during the uprising that is Grindelwald’s war and WWII.
After the war, after Newt and Tina return from the frontlines (they are both called to serve, in their own way; leaving their son behind is the most difficult choice they’ve ever had to make), the four of them buy homes on the coast of England (Dorset, to be precise) and raise their families together.