Interesting how some of X's components defy analysis. I'm guessing that those particular components need to avoid damage, then. Although I guess the only time X really got badly damaged was at the end of X5 (and Dr. Light magically fixed him somehow, so that's kind of a moot point)
I don't think the virus could have come from X. The potential to think for one's self completely, and thus the ability to consider harming humans came from X. I'm thinking that the virus came from Zero and alters the thought processes of a reploid so that the consideration of harming humans becomes a certainty. Zero's made for destruction, but I think it'd also make sense if he was designed to incite others to destroy. But that's just my theory that I came up with in the last 2 minutes XD
I know that MHX made a big deal about X's ability to worry. And I've heard some people even refer to it as the "suffering circuit," but I dunno. I'm kinda confused about all that. I just think that due to Dr. Light's tests, X has an inclination to worry about his actions than other reploids who weren't put through the same tests? Just another theory, though.
As for putting the two of them together... I've always wondered if that's just what Omega from Mega Man Zero 3 was. His second form had a part that resembled Zero, a part that resembled X, and a part that was Omega himself. But then again, Omega's body seems to just be a container for the original Zero and his "real" body. So I dunno. Omega kinda confuses me ~_~
The fact that they complement each other is just one of the game's big ironies, I guess. I love friendship dynamics that work like that, though :D
And once again, thanks! I've started working on Zero's pages, but so far I've only managed to translate the paragraph on the first profile page x_x Ah well, I'll see how much I can do.