Sort of piggybacking on the Nemona talk, I kind of like the Academy Ace Tournament as a story-element tying the post-game battling a bit into things. It feels like a natural conclusion to everyone's arcs and needs that you spent the Treasure Hunt resolving, then bringing together to interact in The Way Home.
Nemona: After making one friend with you, she gets to a rocky-but-ultimately-successful time with Penny and Arven, and then organizes an event that the school loves and matches up with her borderline-obsessive Battling Hobby. It gives her a venue to make new friends around a subject she knows well rather than being the battle-freak Student Council President that no one knows how to approach even if interested.
Arven: He's come across as abrasive and secluded until you get to know him a good way into Path of Legends, my guess because he has attachment issues after his parents vanished and his only companion in Mabosstiff got injured horribly. Helping him confront and heal those emotional wounds and find a new support system with you guys, he starts to exhibit healthier social behavior, participating in something as public as the AAT despite (by dialogue at least, so disregard his in-game difficulty for now) not being much of a battler. He even goes so far as to give it a nick/alternative name that everyone clearly endorses, which feels like he's more at home finally interacting with people again.
Penny: Penny's less personal since she's still a bit of a shut-in, though coming out to participate in the event is a step up for her regardless. More importantly, the Tournament gives the students something to prep for in battling, ensuring that the Team Star Bases serve their "community service" time as training facilities, and gives the student body a reason to visit them and start interacting with the Members again. Given Team Star were bullying victims it probably also helps ease them back into socializing if it happens on their turf instead of returning to the Academy immediately.
In one of her pre-battle cutscenes she all but outright admits that she's stalking you.
Having a battle hyperfixation is cool but I'd prefer if the autistic rep wasn't also characterized as a massive creep. Kinda undercuts it, you know?
I mean Nemona's not exactly subtle or withdrawn about how fixated she is on battling as a hobby, nor her investment in you as her rival, so most of the other characters in the game are aware of it and seem supportive or at least amused by it rather than concerned. Whether or not you or other players read her that way, the narrative clearly isn't trying to characterize her behavior as creepy, at most an overly-energetic handful that's still ultimately a positive presence to have around.
And this is much more a personal experience, but I find when people read into a character as "autistic" rather than just creepy or poorly written, there's usually a positive reception behind it, be it fandom (Seto Kaiba is affectionately called "the most autistic man in the world" by Yu-Gi-Oh fans, while being the most memetic/enjoyed part of the cast) or praise of writing for those traits fitting the bill effectively (as I see with L from
Death Note for example, as a poorly socialized, highly obsessive, but also incredibly intelligent detective), since they don't want to assign that moniker/claim the character as part of that banner if they think them a negative depiction. I don't tend to see people who interpret Nemona as Autistic from these traits also finding the traits as off-putting, or at least outside of realistic levels, especially since they're depicted as giving her trouble and not something brushed off for those difficulties either.