Oh, oops, that reminds me - I meant to respond to the question of Alder, Iris and Diantha, but I seem to have overlooked it!
(While my intentions in writing that were a bit different from yours,
Pikachu315111, I appreciate that you gave your own interpretation! I always love seeing what other people have to say about stuff like this!
Also, I've heard theories about Plumeria being related to the former Ula'ula Kahuna before - I had heard it proposed that she was their daughter, for example, although a Captain probably makes more sense since she gives you the Poisonium-Z - but I had never made the connection between her Poison specialty and the tapu! That's super interesting - it is both the only weakness all four of them have in common and the only double-weakness of Ula'ula's own Tapu Bulu! That's a really cool observation!)
But yeah, here's what I was thinking when I said that, at least:
In Unova, pretty much the center of the story is the idea that, even when people or ideas seem to be in conflict with one another, a) they often aren't so irreconcilable after all and b) there is more to be learned by being open to others' opposing ideas and embracing them than by staying rigidly in your own beliefs; even if you don't outright change your mind or meet halfway every time someone else has a different point of view, you can come to a more nuanced point of view and a deeper understanding of the world than if you refuse to listen to anyone but yourself.
This is pretty much
everywhere in these games. It's in the mascots (the values they represented seemed to be so irreconcilable that they split from the original dragon, but N realizes in the end that in order to change the world, they're meant to coexist rather than to destroy each other), it's in the "truth and ideals" dichotomy (the point of this is that they're not meant to be in opposition at all; changing the world takes both an understanding of it and a desire to make it better, not just one or the other, and both rejecting ideals because of the way the world is and rejecting the truth because of the way the world could be will get you nowhere), it's in the core conflict of the games (Team Plasma tries to frame humans and Pokémon as being better off apart, but they're actually at their best when they're working together and able to grow in tandem), it's in the way other characters engage with Team Plasma (Burgh in particular highlights this well: he mentions that by taking Team Plasma's message into account, he came to reconsider his relationship with his Pokémon and actually ended up closer to them than ever)...
This same theme inspired the region - with its clearly divided segments and its iconic bridges connecting them - and the starters - all of which are based on distinct, non-American cultures in a reflection of Unova as a "melting pot" - and Generation V's Pokémon in general - both the choice to have no older Pokémon (making them appear new and different) and the frequent parallels to older lines (making them more similar and familiar than they might appear at first glance) work together to create this effect.
So yeah. That's the point of Black and White.
In Black and White,
Alder is the character who is most in touch with this philosophy. He more specifically engages with the relationship between people and Pokémon (which is the center of the conflict of the story) in a way that offers him a perspective no one else could share - after losing his first Volcarona to illness, he learned firsthand that there's more to life with Pokémon than being strong and winning, and that triumphing over your opponents and proving your strength is not as important as learning from each other and trying to savor every moment of life.
His central philosophy and background are both directly relevant to the conflict of the games and reflective of the aforementioned core message of the story, and he uses them to communicate this message to Cheren, to N and to the player throughout the game.
Meanwhile, while many people considered her to be an out-of-nowhere choice of Champion,
Iris is the perfect successor to Alder.
As established, a recurring idea Alder raises in Black and White is that the point of
battling is for Trainers and Pokémon to have fun and to learn from their opponents rather than being caught up in winning or losing. In his establishing scene, he even shows this to Cheren by having him battle two young children who go on to do nothing but celebrate how much they love their Pokémon and how much fun they had even after being defeated.
As Champion, Iris takes
exactly this stance - her pre-battle speech is all about how she wants to grow, learn and get to know her challengers by going all-out against them in battle, and even when she's defeated, while she's disappointed that she lost, she instead focuses on how happy she is to have battled the player and their Pokémon and gotten to know them in doing so.
(And it doesn't hurt that she's also a little kid herself, which harkens back to the very first time the player meets Alder in both campaigns. That's a bit less about Unova as a whole and more about her role as Alder's successor specifically, but I think it makes her an extremely fitting choice as Champion for B2W2.)
I think this same message is most explicitly shown in a quote from post-character-growth N (for that matter, he's another acting Champion of Unova) in B2W2: "Pokémon battles decide winners and losers, it's true. Yet they do so much more. Your Pokémon! You! Your opponents! And their Pokémon! Everyone can see what wonderful things the others have to contribute! That's right! Accepting different ideas--different beings--changes the world like a chemical reaction! Pokémon battles are like a catalyst: a small component that leads to big changes!"
Coming to understand the relationship between humans and Pokémon, the way they can learn from each other and the good that comes from battling and growing together is largely the point of N's arc in Black and White - hopefully it's easy enough to see how significant it is that this is what he considers the culmination of what he learned and that it's exactly what both Champions of Unova embody.
With respect to
Diantha... well, I can't argue with that - she
is the most underutilized Champion in the series and has pretty much no role in the actual plot.
All the more reason we should've gotten a Z - does anyone remember how small Cynthia's role was until Platinum saved her??
That said, since talking about story
themes and not just plot relevance
(I mean, I think you knew that and you were just making a joke, which is fair), I'm still going to explain why I think she embodies Kalos well enough - but yeah, I don't actually like her as a character either, haha.
Anyway!!
What I personally understood to be the main message of X and Y is that
beauty is change. Just as Black and White's villains were in the wrong because they wanted to force people and Pokémon to separate, X and Y's Lysandre wanted to force the world to stay the same forever, with his intention being to keep it from decaying so that its beauty would never fade. X and Y also put a bit of focus on how terrifying and awful immortality would really be - AZ spends three thousand years suffering and alone, "condemned to wander forever," and while Lysandre's goal (at least in X) is to give immortality to himself and Team Flare, even he ultimately uses it as a threat against the player and their friends after being stopped: "I shall grant you eternal life! I'll give you the pain of endlessly waiting for a beautiful world to finally be built!" The prospect of living forever is meant to come off as nothing short of
terrifying.
Diantha is the counterpoint to all of this - the one who tells us how important change really is. The very first time we see her, she's debating with Lysandre, and while he
expects her to
wish she could stay young and beautiful the way she is, she dismisses the notion out of hand... the very first quote she has in the entire game is this: "What a strange question... Why would I want to play the same old roles forever? Youth may be beautiful, but it's not all there is to life. Everything changes. I want to live and change like that, too. So I look forward to playing different roles as I get older."
She also strongly embraces the idea of "bonds," which is another recurring idea in X and Y (mostly for its importance to the mechanism of Mega Evolution) - the second time she shows up, while Sycamore only brings up the bond between Trainers and their Pokémon, she explains how bonds relate to her career of acting and suggests that they're important for everyone. As an extension of this, when she trades the player her Ralts in the postgame, she also makes a point of considering how the traded Pokémon must feel, addresses it directly and promises not to the player but to the Pokémon that she'll take good care of it - which seems like it should be completely obvious, but
no one else ever does that, so it's another way to highlight how empathetic she is and how important bonds are to her.
She... doesn't really show up much more than that, haha. On one hand, that's pretty obviously a bad thing - she
does less than any other Champion, and she's totally irrelevant to the story itself - but on the other hand, when basically every word that comes out of her mouth is something about the main ideas of the story, you can tell that at least the intention behind her was to act as an embodiment of those themes and a role model for the player in the same way I've suggested of Kukui, Iris and Alder.
Okay, I did my best - there's my take on how these Champions are supposed to represent the main themes of their games!
