Eh... okay, I don't completely disagree with you here, but that's not to say that I'm bobbing my head up and down, either. I'm completely and totally bored right now, so if you actually want to listen to somebody who only has half of a brain argue pointlessly with herself, read on. xD
One, I actually do find the idea of aging and decommissioning the Kids Next Door to be an interesting concept if written well. I mean, think of the possibilities-- you COULD just write about them and never have them remember (or at least comment on) the KND, but that, like you said, would be like you weren't even writing for the fandom anymore. Personally, I find it an interesting concept if and only if (not including a few stunning exceptions I've read out there before) you tie the fact that they were decommissioned from the Kids Next Door into the story. You could give them back their memories and have them cope with it under strain from a KND-involved situation; you could have them be recommissioned for a mission and deal with their love lives simultaneously (if we're still talking about romance stories, that is); you could have one member remember the past and the others not (I'm actually planning a story that loosely follows that concept at the moment); et cetera, et cetera.
As for changing their personalities-- okay, that I mostly agree with you on. I mean, I admit to being a hopeless 3/4 fan, but if you decide to make Kuki and Wally into completely different people and just stick them together because you like the number 34, I strongly disagree. Unless, of course, you had them acting how they would act if the show portrayed them as teenagers, but they were actually just faking it due to a variety of potential circumstances... but I'll get to that later.
Back on topic, it's okay to change them a little because they'ev been decommissioned, but if it's a radical change, then just no. Why do I say that? (Okay, this is just MY view on it, and my views are usually wrong, but it makes sense to me, so whatever.)
Remember how in ZERO, Nigel's dad acted a ton different than he did after Nigel used the recommissioning module on him? I like to explain that by recalling the nature of decommissioning. Your personality is partially determined by your genes, yes, but the environment and experiences you go through play a huge part in shaping your personality. If you suddenly forget the reasons for those changes, to you, it's like they never happened at all; how can you be shaped by something that's never crossed your mind to be possible, let alone have actually happened? So that would sort of undo the personality maturity you went through, meaning that your personality will turn out how it would have if the Kids Next Door had never happened to you.
For example, take Wally-- in ZERO, Nigel said that he saved him from bullies on his first day of school, right? I assume that, subsequentially, Nigel and Hoagie (already friends from kindergarten) befriended him, meaning that this was the point at which he befriended his future teammates
whom he won't be able to remember. Now, if Wally needed help to keep himself from being bullied back then, that obviously (to me, at least) means that, before he was able to fight back, he was maybe sot of shy, timid, or passive.
As a teenager, he's not exactly going to burst into tears whenever someone calls him "squirt" because, A, he's matured since he was six and, B, he'll probably be able to recall that he hasn't been bullied since then, but he doesn't know why, and he sure as heck doesn't know that he's a bully himself because that was pretty much related to the KND (it was because of being saved from them in the first place and realizing that he doesn't have to be a victim of them-- and anyways, think of MATADOR, BULLIES, etc.). But I'm guessing that, after being decommissioned, it would be plausible to write him as being sort of shy but sticking up for himself (though not to the extent that he used to) when teased or picked on (if that ends up happening, that is). You could take it in a different direction and have him realize that he lost his memory and be mad about it because his personality tends to have him overreact and not think before acting while reacting solely to his emotions and therefore lash out or something else, too-- I'm just giving examples here, not dictating the KND gospel or anything. xD
If you were going to alter their personalities on those premises, though, you'd have to explain in the story (or, if you can't figure out how [but I recommend that you do before you write it], in an author's note) why they are the way they are in your writing instead of reflecting the personalities that they displayed as ten-year-olds. It's unacceptable to just randomly have them acting differently without saying why.
Do you see where I'm coming from? No? That's what I thought, but oh, well!
Moving on...
Because everything I'm about to say (or most of it, anyways) is purely hypothetical and doesn't reflect how I feel about the Sector V characters, let me start off by saying that I agree: having the KND act maturely instead of how childishly that they do in the show is definitely OOC and doesn't portray their characters accurately. With that said, I will continue to confuse my brains out with my discombobulating logic. Yay!
The thing you said about mature behavior only being justifiable by family life circumstances that have been proven to not apply is, as far as I can reason, one-hundred-percent true. I won't say WHY because you've already done so, and anyways, I'm not a psychiatrist (and probably never should be, even though I come up with all sorts of psychological reasons to explain reasons for the annoying behaviors of my peers... but I'm not here to talk about my personal life, so let's move on), so I shouldn't in the first place. However, this is fanfiction that we're talking about. It's not like we're writing new episodes or anything-- if that was the point of fanfiction, I'd be forbidden from writing it because I stray off of what's canon into my own little sub-concepts that will never happen but make sense using my weird reasons
all the time. Fanfiction is fiction written by fans for a fandom-- can't a writer use his or her imagination?
What I'm trying to say (and failing miserably by rambling so much) is that, while mature situations and behaviors in the lives of the KND would never happen in the show, there's nothing wrong with writing about them as long as the writing is done well. Let's go back onto my personal life for a really quick second (I PROMISE this is the last time! xD), shall we?
[insert really big rant that I deleted for the sake of your eyesight here]
xD
To summarize it, though, I'm thirteen, but I get along better with adults than my peers because I think more maturely than my classmates do (and no accusing me of having a big ego; this is what grown-ups say to me, not what I say about myself). My peers, however, have no idea of this because I get uncomfortable when I'm acting more mature than they are because I don't want to make them feel less than me or anything because I don't think of them that way, so I usually just act as immaturely as they do, meaning that they don't have a clue what I'm really like (aside from my hobbies-- I've had to repeat myself constantly in saying that, no, I DON'T want to go shopping because I
really, really, really hate shopping and the likes). As for angst-ridden kiddies-- that's my business, and I'm not going into it, but trust me when I say that it can be in kids' natures to not be carefree or happy or whatever. So if you're having Kuki, like, be all suicidal or something at age ten, that's taking it maybe a step too far, but it's not a very big step. End of story.
Anyways, if you're totally obsessed with angst (like I am-- yeah, yeah, sue me, but I LOVE it because I am WEIRD like that xD), it makes sense to have the KND be mature in private as long as you explain how it's plausible that they're like that (am I getting repetitive here? xD). However, if you randomly have them acting more grown-up than they do in the show around each other, I don't sit well with it (unless some tragedy happened and they're reacting to it, but that reaction wouldn't be permanent, anyways, so you'd have to have them back in character once they've coped with it enough to go back to the way they normally are). Random maturity is OOCness. Maturity on a personal level but not a public/social one is not, and if you're having a serious romantic relationship between two characters, it would have to be because they're willing to open up and be open about their thoughts and stuff instead of just randomly deciding, "Hey, let's be in a committed relationship!"
My fingers are literally starting to sting a little from all this typing, so I'm moving on, unless you didn't get it and want me to explain myself again. Fun, eh?
Luckily, my fingers aren't going to be taking much abuse because I fully agree with you. Sorry, guys, but I'm not partial to damsel-in-distress romance (or the other way around) unless one of the characters is in distress but in a relationship that wasn't formed due to it (and even when that happens, if the "strong" character saves the "weak" character because said "weak" character is incapable of being independent, then no-- just no). The annoying thing about stories like that is that, usually, it's the girl that needs saving by her strong, larger-than-life crush who apparently owns my socks off-- and the girl, like, WANTS to be saved and doesn't want to even attempt to fend for herself. That's sexist, if you ask me, and like saying that girls can't take care of themselves. Okay, so maybe I'm biased about that one because I'm a girl with the most feministic sister on the face of the planet who rants about female equality every single second I'm around her, but I'm not off base here, so what's wrong with my opinions? xD
Okay, I'm done arguing with myself now xD. In case you're curious, yes, I read the whole thread... but if I type anymore, my fingers may become seriously injured. Feel free to disagree with me (though, knowing me, I won't be able to come up with anything to counter what you've said, so... heh? xD)-- I'm just stating what I think and what I think alone, and I'm perfectly happy to agree to disagree. ^^ I just felt like rambling, and I
did say I was bored, didn't I? xD
Edit: I forgot to mention that this all depends on how well you write. If you're a poor writer, you probably can't pull off the stuff mentioned, but if you're a good writer, you probably can.
Moving on...
So many interesting posts. But my eyes will bleed if I read every single one of them 
?! Where's the flow of events)
