Granted, but consider what Flame was responding to. A "Classic Skin" on Sonic doesn't fix any of that. There will probably be a million reasons to complain about the so-called STH4, but I don't see Sonic's eye color and buckles as being one of them.
Hey, the clash of play styles is what makes character selection so interesting. The only problem is when certain parts of the game are much too hard for one of the characters, which is why some people didn't like MegaMan & Bass.
I'm referring to when the difference is so drastic as to warrant a different level design. A "true" Sonic level design, assuming of course Sega will actually do a decent job of putting their money where their mouth is, includes a lot of stunts that I don't see as fitting for Mario. Granted, with Amy doing loop-de-loops, Sega is pretty loose on that point, but still.
Heck, for that matter I don't think it'd work very well the other way around, either (referring to the "Sonic in SMG2" rumor
above). 2D Mario is pretty basic platforming and friendly to a wide variety of characters, but 3D Mario is about sandbox fetch-questing at a lax pace while you drool over the environment. That's not a play style that Sonic belongs in. Though, I must admit, I'd be curious to see the press's reaction if that ever actually happened.