First, here's a full list of events in Frozen which are relevant to the discussion of why I thought the film-makers were foreshadowing a different "twist". Timestamps are very approximate but should be good enough to find the relevant scenes. For the actual discussion, skip ahead to one of the other sections.

17:00 Hans and Anna meet almost exactly 17 minutes into the film. She collides with his horse and the fall around awkwardly into a row boat in a fairly typical Disney movie meet-cute. Hans finds out almost immediately that Anna is the younger of the two princesses of Arendelle, and that her older sister, Elsa, is difficult. At just before the 18 minute mark, after Hans has apologized for knocking into her, Anna says, "No, no, it's fine. I'm not that princess. I mean, if I were my sister Elsa – yeesh." (well, maybe it isn't 'yeesh'. Some sort of incoherent noise of warning and disapproval, though).

18:32 At the end of the conversation, Hans falls into the harbour, and the row boat falls on top of him. We see him watching after Anna with a goofy,happy expression, in a situation where nobody else can see him – this appears to be a genuine reaction as there is nobody to put on a show for.

22:42 At this point, Hans and Anna interact in various ways (dancing, talking, etc.) that make him look unusually accommodating towards her. Specifically, at 22:57, she bashes him in the face and he laughs it off.

23:19 Anna and Hans discuss their siblings. Hans mentions his 12 older brothers and again, Anna describes Elsa in negative terms.

23:41 The start of the "Love is an Open Door" sequence (which is my favourite of the songs in the film, if you were wondering). Anna asks if she can say something crazy; Hans says he loves crazy. I would also direct your attention to Han's line 40-odd seconds in, when he sings "I've been search my whole life to find my own place," and gestures to the kingdom, before adding "but with you I've found my place."

24:43 Still in the song, this implausible interchange:

Hans: Well, I mean it's crazy,

Anna: What?

Hans: We finish each other's -

Anna: Sandwiches!

Hans: That's what I was going to say!

Following an accepted marriage proposal, Anna takes Hans to meet Elsa.

https://youtu.be/kQDw88hEr2c

26:16 As part of the discussion regarding their engagement:

Anna: Would you move here?

Hans: Absolutely

The sisters argue about the wisdom of a first date engagement, which ends with Elsa publicly using her ice powers for the first time.

27:34 Look at Hans' face here. Anna has just used her ice powers, and he looks like a man who has just had a revelation. Something here – Elsa, her powers, both – has completely fascinated him.

28:25 Wessleton calls Elsa a monster; Anna and Hans run after her anyhow. As it starts to snow, at 29:37, Hans makes a point of asking Anna "Did you know?". Wessleton repeats his various accusations, and claims that Elsa tried to kill him. Even before Anna speaks up to defend her sister, Hans defends Elsa and appears to try to calm Wessleton, by saying, "you slipped on ice," in a calm, measured tone.

49:40 by this point, Anna has gone after her sister, met Kristoff and Olaf, sung a couple of nice duets, etc. Hans, meanwhile, has been left in charge of Arendelle – and he's doing a great job. He's arranging hot food and warm clothing for the people, apparently maintaining law and order, and generally behaving like a sober, hard-working administrator.

50:40 About a minute in, Wessleton says that Anna is conspiring with Elsa, whom he describes as a 'wicked sorceress'. Hans shoots this down immediately, saying he is in charge and will protect Arendelle from treason.

At this point, Anna's horse runs down the mountain. Hans calms it, and vows to go after her.

1:09:37 Hans and the guards approach the ice castle. When Hans first sees the ice palace , note his reaction; he is impressed, possibly fascinated. As he dismounts his horse, he orders that no harm is to come to Elsa.

1:10:22 Wesselton's men take advantage of the battle with the large snowman ("Marshmallow") to enter the ice palace, crossbows at the ready, alone. Hans and all of Elsa's presumably-loyal guards are left behind. Hans looks dismayed by this.

Elsa disables one of Wesselton's men, and begins to force the other to his death by pushing off a balcony with ice.

1:11:47 Hans successfully talks Elsa out of murder, by appealing to her better nature - "Queen Elsa! Don't be the monster they fear you are."

1:12:02 When the apparently disabled guard turns out to be not so disabled, and tries to shoot Elsa with his crossbow, Hans redirects the weapon so the bolt is shot towards the ceiling. Now, much has been made of the fact that he looks up first, and that a part of the ceiling decoration /chandelier falls and nearly hits Elsa, but he'd have to be an implausibly good shot to hit what appears to be the only weak point on the ice structure, a point that appears to have the exact same width as the arrowhead and, based on the shape of the decoration, doesn't actually seem to be visible from the ground (note, too, that the camera shot towards the chandelier appears to be from Hans' point of view).

https://youtu.be/afnhCvicqdI

1:12:30 Elsa comes to in a cell in Arendelle. Someone has carried her down the mountain and placed her on a bed with a pillow and a blanket. She is not being treated unkindly by her captors.

1:12:50 Hans comes into the cell. Elsa asks "Why did you bring me here"; Hans says "I couldn't just let them kill you," and tries to reason with Elsa, begging her to bring back summer. When she says she can't, he looks surprised and concerned, his eyes growing wide and then narrowing again in resignation.

1:14:59 Hans wants to go out to find Anna, but is talked out of it by the various dignitaries in Arendelle, being told that if something happens to Anna "You are all Arendelle has left."

Seconds later, Anna arrives, demanding to be kissed. They are left alone, he carries her to a chaise longue, they he leans in to kiss her, the music swells, and, well, there's a twist, rather than a kiss.