I've seen that art, but I never bothered to save it...
Inafune meant to end it at X 5 then capcom went and created x 6 without him knowing about it.
*smacks Obdulio with his magical talking fish*
First of all, Inafune didn't produce X5 either, he was merely consulted with it. Secondly, he was describing his initial reaction WHILE THE GAME WAS STILL IN DEVELOPMENT. As we have been over several times already, Z1 in its finished form makes no sense following X5 directly. This issue was spotted and addressed before either X6 or Z1 saw release, and pre-release concept =/= canonical continuity. So that point is completely moot.
Legends: Sheer number of easter eggs along with everything else. You really have to twist a lot of minor plot elements around to make even a small connection to the series at that point. Author intent is clearly to make a new continuity.
That something is not established does not mean that it's invalid. You're merely justifying an assumption, but your perception of what is likely by no means indicates author intent.
Some of the easter-eggs you pointed out (cartoons and comics) are from L2, the same game which also established Irregulars and Elysium, which X5 references. By then the connection is far more solidified than L1, even if still vague, and as such your argument is invalid. The only easter eggs that I recall in L1 are the X-Buster and Z-Saber (Zetsaber) items, Roll, and Wily's boat shop (I'm not counting MegaMan's name because that's the name of the series). However, an easter egg does not constitute an AU. And I'm not sure if this is exclusive to the U.S. or not, but the game even breaks the fourth wall with its own title if you examine the shelves.
Author intent is that Legends is "disconnected" from the other series in that there was no clear story-relevant tie-in, but an AU means that it can never exist within the current continuity due to conflicting events, there are no such events within Legends. Legends has no stated timeframe, and takes place on a flooded planet which is a common "doomsday" scenario, and also is in a world where ancient technology surpasses the present. So not only is the claim of an AU, even at L1's timeframe, complete fanon, it is also highly questionable considering that the timeframe if AT ALL relevant to Earth appears to be an extremely distant future. All of this at the time of L1 is unconfirmed, possibly unaddressed by the devs, but that doesn't make it invalid.
Serges: Ah, well, I'm talking a more literal "is Wily". And, back then, it would be based on his appearance and "scientist" status than anything else. Maybe that's where we're going wrong here. As for Isoc, I never brought him up because I do believe there's enough to say that he is Wily.
Well, Serges is as much Wily as Isoc is. They are Wily for the intents and purposes of the story, but they are also Reploids. Whether his digitized consciousness is jumping ship, or they're remote avatars, or whatever the hell the details there are, that's a whole other bag of chips.
But as for Serges, well ... when you have to connect the dots like that, it's where canon crosses the line and becomes fanon, IMHO. If and when Capcom confirms it, I think you'll have a pretty solid case for it being part of a master plan. But, right now ... it's too vage to call (by a thin margin, as I admit it makes sense). And since Serges is unlikely to ever be followed up on again, I'll err on the safe side and say that he is not Wily.
While we're on the topic of "connecting the dots", here's the tidbits that didn't make it to the U.S. In other words, stuff that the Japanese (you know, where these games come from) had from the word go:
-X2, which introduces Serges, happens to also include the first "Wily hint" of the X-series, which is to say the first syllable of his name when Sigma references Zero at the death speech (slightly less vague than our version which offers no name fragments, merely a "Doctor"). So if you're thinking who Sigma is referring to there is something retroactive after X4/Power Fighters, think again.
-Japanese books compare Serges's super-genius nature to the "legendary scientist" of old.
-In the Japanese script, Serges is the *ONLY* character besides Light to ever refer to X as "Rockman."
-Also in the Japanese script, Serges is the only character to reference Dr. Light as X's creator. And he brings that up because he has issues with being beaten by a creation of Light's.