What if Tohru Honda and Nagisa Furukawa SWAPPED PLACES??? (Anime Theory)
I originally came up with this concept after reading a Reddit thread asking if Tohru and Nagisa would be the best of friends (and the answer was absolutely, they're two precious angels). I can't find that thread anymore, but it prompted me to think what might happen if they switched places. Despite making almost 20 minutes of in-depth analysis, I failed to consider what Uo-chan and Hana-chan would think of Nagisa. I'm thinking they'd probably have similar vibes, assuming of course Akio replaces Kyoko as their guiding compass (though Uo-chan has no reason to take any interest in Nagisa because she only followed Tohru home to meet the Crimson Butterfly. Hana-chan only took notice of Tohru and Uo-chan because they stuck out, and she only sat down with them because they were so insistent. Nagisa is definitely not that stubborn when it comes to making people do things they don't want to, so it's unlikely they'd even become friends with Nagisa in the first place). Also, the only way for the Somas to heal as quickly as they did with Tohru would be for Akio to get directly involved -- which I go into in this video. He'd probably also not take too kindly with Shigure flirting with Nagisa, whether jokingly or not. And speaking of Shigure, it's possible Kyo won't ever go to live with him and Yuki, considering the whole trauma incident with Kyoko doesn't take place.
I also didn't take into account how Sunohara might be affected by this new dynamic with Tohru in the picture instead of Nagisa (he'd probably be terrified of Kyoko if he was caught hitting on Tohru in front of her. Add Kyoko to the list of violent girls like Tomoyo and Kyou, lol). Club activities would probably not be a thing with the CLANNAD characters anymore because Tohru wasn't interested in club activities in Fruits Basket. At the same time, plays like It's Cinderella-ish might be more prevalent in this new Fruits Basket universe because of Nagisa, assuming she doesn't put off her own desires for the Somas' sake. The Soma curse on top of the unresolved issue of her parents leaving their dream jobs could crush her aspirations for good if Kyo and the others don't actively support her and convince her otherwise. But if they're still dealing with their own trauma, they might not think to do so. Overall, the interactions between Nagisa and the Somas would be more like Fruits Basket Another rather than the original series because Nagisa is more the Sawa type -- someone who apologizes profusely for everything including existing, like Ritsu. The difference here is that the curse was already broken in Another. Though that's not to say Nagisa can't have the same effect on the Somas as Tohru; it just might look different, and the Somas would actually have to read the room just a little bit more as opposed to Tohru using her extroverted nature to slap kindness right in their face at every turn. As Tohru herself said, people's kindness looks a little different from each other. Nagisa's kindness is similar to Tohru's -- where she's willing to be unhappy forever if it means making others happy -- but still just a little different, and it might not be quite as obvious. That said, Tohru's kindness was sometimes overlooked, such as when she told everyone to go enjoy New Year's with their families. Fortunately, many of the Somas are intuitive people because of the cryptic nature of the curse. And if Akio is indeed involved with Nagisa's dealings with the Soma family, he can also help spell things out a little.
On Tohru's side of things, I don't think Tomoya will have to pry out Tohru's confidence nearly as much as he had to with Nagisa. This would make a Tomoya that's probably a more well-rounded adult like in the Tomoyo route, but still with a somewhat aimless adult life. Tomoya's and Tohru's arc would really shine as a college-age-to-young-working-adult slice-of-life-type anime rather than a high school drama. Kyo, meanwhile, wouldn't be so reliant on his hate for Yuki because Nagisa gives him something to work towards, both as a friend and as someone who just tends to need the support of at least one other person to see her aspirations come to fruition (this is primarily because it's highly speculated that she, as well as Fuko and Kotomi, are autistic and aren't as self-sustaining as Tohru. I mean, can you imagine Nagisa trying to do the whole living in a tent thing? I don't see that going well at all). Nagisa's slight dependence on others would give Kyo a more healthy outlet for his energy and effort than to constantly try in vain to beat Yuki. Between her, Akio, and Kazuma, maybe we'd end up with a Kyo that acts as a sort of Tohru to the other, "legitimate" members of the Soma clan and helps them break the curse.
Lastly, I didn't go much into Nagisa's dynamic with Yuki. He definitely wouldn't see her as a mother, that's for sure. I think actually the roles might be reversed. He'd likely see someone HE wants to take care of.
Welp, that's all from me for now, lol.