Tobi= Madara Uchiha = Danzou
It seems that way anyway. I don't see any canon contradiction in it, that I can recall anyway.
1. Village destroyed? Danzou/Madara is very pro-war and quite likely believes that the village needed to be destroyed to wake them up from their complacency. Which oddly enough, is similar to this recent (a few days ago) statement from a former CIA agent.
Pain's attack certainly was like a "major weapon". How is did Danzou get elected? He made the case that he would protect them. How convenient for him to set up the very attack that gets him elected.
2. He told Sasuke to kill the other Kage. Why? So he can eventually be the leader of every country, or at least have a grand old war. The fact that he ordered Sasuke to be killed is fine, because he was upset at Sasuke for failing him coupled with that he's a eventual threat to Madara.
3. The last page of the newest chapter. He's lost his vision in is right eye, probably like it says happens from using the Mangekyo Sharingan too much. Also on this last page, he's planning to kill off anyone who might know anything about him.
4. Root, emotionless supersoldiers, tongue tattoos, forming a powerbase within "enemy" territory.
AGAINST:
In some filler episode of the anime it shows Danzo as a young guy or something, but it's like in the last 2 minutes after that credits thing and very non-canon.
NOTE: I'm not saying that I think Danzou was plotted to be Madara from the beginning, I think at some point it just happened. But, if it was planned that far ahead, that's cool too.