Well I have been thinking about this for a little bit and finally have come to a conclusion. It's something so obvious when you stop and think about it its hardly even arguable.

:The Truth Hidden in Orchimaru's Scroll :

- First thing we need to clear up is the Kabuto factor. Orochimaru never planned to die and have Kabuto take his white cells an join Akatsuki that was not apart of his plan so the scroll in no way has any connection to anything Kabuto is doing, Itachi was brought back for the key purpose of dealing with Kabuto and so he shall.

- If everything went according to plan Orochimaru would have taken Sasuke's body and would have what he wanted the Sharingan in a Uchiha body a direct descendant of the Sage of the 6 paths. This is where Orochimaru's genius plan comes into play to take control of the battlefield.

Akatsuki has one asset which is the key to their entire war plans and it is so obvious and has been there from the beginning of Shippuden. Take a wild guess what it is.....???

Gedou Mazo !

* The statue contains the 7 Tailed beasts the Key to Tobi's plans of reuniting the 10 tails

* The statue also is the source of the chakra that makes up the White Zetsu army

- I think the scroll is a method for Sasuke to synchronize and use Gedou Mazo in a way perhaps we have not seen before. We do not know of its full capabilities so it may have secrets we are unaware of. This fits perfectly in a way with what Tobi wants as he displayed interest in wanting to make a pawn of Sauske by hooking him up to the statue but hesitated because he wasn't sure if he could manipulate Sasuke well enough to make him do what he wants.

- I think there are some hidden factors here for one controlling Gedou Mazu might require one to be a descendant of the Sage of 6 paths. More than that it may require the Rinnegan or rather not so much the eyes as the strong vitality of the Younger brother plus the powerful mental energies of the older brother. I mean look what happened to Nagato who was an Uzamaki when he hooked up it seemed to drain his lifeforce so imagine what would happen to someone who lacked that strong lifeforce. Its possible that trying to hook up to Gendou Mazo is like using the 5 treasures you get drained so heavy that a normal person would die.

In fact Databook 3 seems to back this up:

It's called "Fuuinjutsu - Genryuu Kyuufuujin".

The text says:
"It can be performed by a maximum of 10 shinobi at the same time, that by focusing their minds together can start up the sealing statue. The 'absorbing chakra' radiating from its mouth extracts the bijuu's chakra and seals it. The whole process takes days to be performed by Akatsuki-level shinobi; average ninja wouldn't even be able to summon the statue."

Caption: "The 'absorbing chakra' takes the shape of 9 dragons and seals the bijuu's chakra. When the sealing is complete, the statue awakens."

- Someone else made reference to what Kishi mentioned a while back that when he gives Naruto a power up Sasuke is sure to follow in order to keep them even. After seeing recent chapters with Naruto able to synch completely with Kurama & perform the Bijuu bomb able to match a combined Bijuu blast from 7 tailed beast, its hard to imagine Sasuke with just Susanoo being able to challenge Naruto.

I think hooking up to Gedou Mazu is the power up Sasuke needs to be a perfect match for Naruto. With the GM at his disposal Sasuke can borrow energy from the statue to power up his Susanoo a challenge Naruto in his full powered Bijuu mode.

There are 2 scenarios from here either Sasuke finds a way to put Tobi in a jam after gaining control over GM or Tobi encourages Sasuke to use GM more knowing that GM drains his life force the more he uses it . Either way the key to controlling the War is Gedou Mazu !!!