Nice read POW.. like always!
- Though I don't see Sasuke getting or using Hashirama's powers. It just doesn't fit.. and remember what Itachi said to Sasuke: Madara is became a shell of his former self, he isn't even WORTHED for wielding the title of a " True Uchiha " anymore.
This means that Sasuke will increase his powers through anger/hatred to another level; and Oro's scroll is going to help him from step 1 to 3. There's a reason why Juugo reacted like that, near that cave. I think that Juugo's powers is very close related to Nature; something close to the lineage of the younger son ( Juugo feeling all in peace with birds flying around him etc.. )
Juugo already have half of his powers to Sasuke, when he was gettin beaten by Killer Bee. Later on; we saw him extract the life out of a Samurai and grew from a child looking person to a grown man. Juugo's sacrifice will be needed, for giving some powers to Sasuke ( which could be written down on that scroll ).
Orochimaru was after the sharingan and needed an Uchiha body. Orochimaru with all his experiments, could have founded a way for evolving Sharingan --> Rinnegan, and it's not going to be Hashirama's powers this time: it could be Juugo's.
That's why Sasuke will not be using Mokuton at all, and too be honest: I don't want Naruto to use it either. You're totally right by saying that it was all a forshadowing when Edo Madara came into the picture and showed off his powers. Everybody thinks that Rasen-Shuriken was too much for Edo Madara, and that's why he used Rinnegan.
Who says that Perfect Susanoo couldn't stop such power?? Rasen Shuriken was so close, so he probably didn't had to for summoning Susanoo; thats why he used Rinnegan + this way Kishimoto made him look fuckin badass when he used Rinnegan after his EMS.
I also still think, that Itachi will give him something with his poke on his forehead; will it be a flashback of Uchiha Massacre, or the Totsuka Sword + Mirror?
Imagine Sasuke's Pefect Susanoo with 4 arms, wielding; arrow, Bow, Mirror and Totsuka Sword.. and lets say that he will get the Rinnegan also. Now, Naruto has to mix his Sage into this Kyuubi Mode and his final power up, will be the soul power of all the other Bijuu's.
I completely agree with you, that Tobi will try to use Sasuke's body for a sacrifice; his plan for reviving Madara back into the picture. And like you said; he could only do that, when Sasuke has the Rinnegan ( without Rinnegan, Sasuke will die immediately ). And the funny thing is: even IF SASUKE gets the Rinnegan, he will still die eventually, because his body doesn't has the necessary nature LIFE FORCE / PHYSICAL POWERS, like Naruto does. This was probably the reason why Edo Madara died back in the days; he became a manipulated version of SO6P.. he wasn't destined.