There is something I noticed from Stella's arc as the potential mother in comparison to the ending of the show. In the later seasons of the show we see Ted trying to be with Robin again, breaking up with Victoria over her and getting her Something Old she had as a gift that he tried to convince Robin was from Barney.
All of this seems to suggest that Ted had feelings for Robin and made the resolution of the finale with the kids stronger.
However, about Stella's arc in the show. First of all, I don't think Ted and Stella had much chemistry. A lot of what they liked about each other seemed forced and the speed of the relationship was going too fast, even if it happened through two seasons. I will say that I feel like Stella could have never been the one Ted ends up with.
But, at the wedding, at the end of her relationship arc. Stella says she'll talk to Robin and he should talk to Tony about not being in the wedding. In response Ted says he'll go talk with Robin and she will talk to Tony. From this we find out two things.
(1) Ted moved on from Robin for good by saying that Stella was the one after she tells him to break it off and he tells her not to be in the wedding. But (2) we learn that Stella still had feelings for Tony and calls it off because she's still in love with him.
However, Ted is telling the entire story, starting from Robin and ending with Tracy, ultimately ending with how he met Tracy, and Ted's kids reply is, "you're totally, totally in love with Aunt Robin."
But the end of Stella's arc makes me wonder. If they were planning on the kids to say that since season two, why didn't they make Robin's attempt to force Ted to call off the wedding work instead of it going the other way around and Stella breaking it off instead?
I get the fact that they wanted Ted to look like the good guy in all of this, especially after he said that he would talk to Robin about it. But if the ending was planned like this since before we got to even know Stella, with the kids insisting that he's still in love with Robin, why would they intentionally set up an arc that proves that Stella meant more to him than Robin?
Looking forward to hearing some fan theories about why they decided to do it like this.