My idea was maybe Madara still has connections in Konoha, Then I was thinking and realized something.. The Root Anbu has been mentioned once and was built up to be this big thing about inner-corruption, but then it was quickly killed off. Why? Maybe because it was giving out hints... so Then I looked back at the Manga pages, to review this time period (The Introduction of Sai Arc) and Saw this----> look at the first pictures i attached at the bottom of this post.
Now, I bet your wondering whats going on here? Anyone Notice how the bandages Cover the same eye as Madara has revealed his sharrigan as? Pretty Odd... and theres never been any reason for Danzou to cover his Eye.
Now I know what your thinking, Danzou = Madara is Pretty Random, Right? Wrong.. Listen to this :
1) Danzou's methods have been declared harsh and rough. Madara's Methods were the same, that caused the fight between him and the first hokage
2) Danzou and Tsunade has a pre-existing Hatred. Tsunade is a direct relative of the First Hokage, therefore Madara could still be enraged about how the First Hokage took his village from Him.
3) The Root Anbu Claims to have the best interest in mind for Konoha, well if Madara/Danzou claims that, he can easily gather up followers and create a rebellion from inside of Konoha to take it over. He Can't use the Akatsuki to do that kind of Damage.
4) Why Return to Konoha? Because It was Madara's Legacy, and Where else to start his world Conquest, but his very own legacy which was stolen from him?
5) Re-look at the facial marks on the first picture, then compare it to this one of Madara :
(look at the second pictures i attached at the bottom of this post.)
The Lines Match Up, as well as the Ears are very similar.
6) Why Wear a Mask As Tobi/Madara? To Hide the majority of his face so that he may move around Konoha as Danzou without arousing any doubts. Why Wear the Bandages as Danzou? To Hide the MS Sharrigan from Konoha Ninjas.
I think its a legit idea, but its only a theory of course. Also, Please No "Thats the stupidest thing I've ever heard " Stuff, You don't like it or Disagree, just post so in an adult-like manor.