nice to see a new theory which isn't just "Naruto is the 4th's son! look at the hair!", but you're wrong in so many levels...
The sharingan thing was one of the more idiotic ideas... you're completly ignoring the fact that Kakashi was once an avenger as well, and that he probably did something indecent (betraying his friends) to get the eye, the idea of Kakashi being married is so out of porpotions...
the Itachi idea isn't half bad, but since i wrote something very similiar at my "itachi is a good guy, while sasuke is an idiot" theory, i can't say it's super original either...
you know what? here's one fatal flaw in the theory... why does the 4th want Naruto back now? wouldn't it be better to take him with him when he supposdly 'died'? that way he could train him into a perfect ninja and shape him as his succsor...
and just the last thing... Jiraya was able to find out that Itachi was part of the Akatsuki orginazation but he couldn't figure out the 4th hokage? and he was his teacher, for heavens sake, he's supposed to know him better than anyone else, and to know his tactics and ways of action...