So first off, Aoyamada-kun was one of my favourite side characters ever. I just really loved him from the beginning on. So.... opinions on him?

But second: Hasn't it bothered you that there is a boy with a name like Aoyama's, looking exactly like him? Didn't you think it was far-fetched?
Well, think back to the vaguely Aoyama-esque alien child again. And to the fact that Aoyama was just a 'disguise'.
It's possible that Aoyama as we know him was based off a random child in both name and appearance, to make him a realistic human. And that's why Aoyama is more or less an Aoyamada clone without even knowing about the other ever.

This opposes all of my headcanons, but the possibility gave me the OMG moment of my life just now.

I used to hate Aoyama back in the day not because I shipped KishxIchigo, but because I saw too much of him in the manga. Like almost every page I would see him and it annoyed me. I know he's Ichigo's crush, but seriously we needed a break from the guy. It most magical girl series we rarely see the main girl's crush. They usually pop out of no where to be the victim of the day.

Now, I have a better view on Aoyama and I actually like his character. Also I do not view him as a canon sue. While the manga explore his character better, I wished the anime did as well. Well, at least his back story. I like the idea that they had Ichigo go to Aoyama for advice in the anime. He does seem like the type of guy you would go to for advice.

You know what's odd even though I ship KishxIchigo one my favorite scenes in the manga is where Aoyama confesses his love to Ichigo under that tree while it's raining. I find it so cute and romantic. The anime ruin the cuteness. >.<

As for Aoyama look alikes in the anime. Yes it is odd to why they have them. I think the only reason that they had that Aoyama human look alike was to have Ichigo think about Aoyama (I never really liked that filler episode). As for the alien look alike, I already mentioned it here on the forum. :P

The scene with Aoyamada always puzzled me when I was first watching TMM. The weirdest thing was that the Mews just went along with it. Like oh okay. That seems legit, you're a carbon copy of some other guy we know, except you're like an inch taller. What??
I'd come up with a theory that Aoyamada was a normal guy, and perhaps his body was taken over by Deep Blue as well, to spy on the Mews that one day. (I don't know why he couldn't just have Aoyama go along with them, though?) Deep Blue has a limited palate of looks for his "disguises", which is why the two looked near identical.
I like your headcanon, though. It gives this underlying eerie tone to things.

Actually TVtropes has a fan theory about this as well and let's not forget Ringo's brother, Mashio, who is not only another Aoyama look-alike but is also voiced by Megumi Ogata.
The theory was basically that Deep Blue created more than 1 body just in-case Aoyama rebelled or something else went wrong.
Speaking of Aoyama, I'm also curious about how much of his original powers he has left. In the manga, he was the one who escaped Deep Blue's palace with Ichigo (he floated down) and he was one of the first to sense danger to the Earth in A la Mode.