Madara's body has been heavily modified in many ways. Since the very beginning, before he even looked at Hashirama's face, he mentioned how someone was able to bring him back "in this state". Since Madara met Nagato when he was young, this means he was an old man when he died and Kabuto brought him back in a young state. Madara awakened his Rinnegan shortly before his death, so at low chakra levels it was useless. This certainly means Kabuto brought him past his prime because for the first time he is giving Madara a chance to sport the Rinnegan properly. In addition, this same page has him say "This is HIS doing...Things must not be going according to plan."...Of course he means Orochimaru, as Kabuto further re-enforces this by saying he is his assistant.
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Now on the page after he summoned the two comets, he says that this is a view he has not enjoyed in a long time. This is because as an old man he would not have had the ability to handle the sage's power. He and Hashirama could rewrite entire maps when they fought, and the way he stated it had been a long time means he did not partake in any big fights in his later years.
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Now, this page here makes it clear Madara took Hashirama's DNA and had implanted himself with it since Kabuto SPECIFICALLY said he gained a PORTION OF HIS STRENGTH. Notice that Kabuto did not tell him where to look but Madara immediately checked that area. This means when he died he ALREADY had Wood Release. My guess is that someone else's DNA does not get revived with you when you use Impure World Resurrection. Basically Hashirama's face is a living being and would have a separate soul. As such, Kabuto had to REPLICATE Madara's procedure and somehow make it work with the resurrected body.
It also seems Tobi has forsaken Madara and tried to take over the Moon's Eye Plan for himself.
Here Kabuto claims Orochimaru was the one who created the face on Harishima's body...So it almost seems as if Orochimaru was the one who originally summoned Madara but kept him in a dormant state.
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The big point is that both Orochimaru and Kabuto could have heavily modified Madara's body, and set a curse mark on it, as well as chakra seals and dampeners to allow the seal to take over. It's okay if you like a character, but with the right knowledge and preparation another one can one up even the strongest of foes. The game is not just about mere brawn. People get offended and attain tunnel vision when it comes to their character being one-upped.