I disagree with the sentiment that Edo Madara is "practically" a SO6P. He is a freak of perfection gone wrong. By this I mean he cannot die, he has some of the most rediculous jutsu's this generation of Shinobi have ever encountered, a near limitless well of chakra, Rinnegan, EMS, the 1st Hokage's Wood Justu and did I mention he can't die? The S06P had all this without the Edo part and also had complete control over the upper doujutsu techniques of Creation, something which I hope Madara cannot attain.
My only thought on how this freak will be beaten is with a sealing jutsu from the Uzamaki lineage, attained either somehow by Naruto or we will have another character added in the future.