I enjoyed all the essays in this thread. Sansa-Sandor is beauty and the beast whIle Brienne-Jamie is reverse beauty and the beast (in looks, not personality)
I do disagree about Arya-Gendry being a romance. I just think both of them are too young. What I see is the potential for romance when they are both older. I think they are perfect for each other and that there is no one else for them. All their interactions seem like actions of children. I don't think they have a brother sister relationship and their bond is deeper than friendship.
What I see is the foundations of a great marriage partneship. They first established respect for each other and then trust between them. They can have disagreements and not let it affect how they feel for each other. At different times they let the other person lead. They have light moments between them and generally like being around each other. They don't like anybody else intruding on their partnership (like Bella or Eric Dayne). They think the other person is attractive. They think about what their future is like with each other and want to be near each other. They also care about each other's safety and do what they can for their friend to be safe. They also care about each others opinion. They also try to make each other feel better.
I do think Gendry saw that he was losing his friend who he cares for and has a deep bond with. He is sullen and upset because he sees that he has no place in her world. That the outside world wouldn't let him keep his friend because of class. Arya considers him as part of her pack and feels that it is a betrayal when he joins the Brotherhood (contrast that with Jon who leaves for the wall. She would miss him and loves him, but I don't think she feels as upset that he left her. Jon's reasons are similar to Gendry's for joining)
I have a soft spot for angry, upset Gendry. His feelings seem believable and real.
I do think they will be together after they reunite. I see it heading in that direction. I like their relationship. It's so rare in fiction and real life. It's a great partnership. I think GRMM spent a lot of time and energy crafting their relationship and setting it up for future payoff. Their relationship is innocent and pure and we don't see that often.