Ok, so I'm one of the few that thought Sasuke getting the Rinnegan was stupid and impossible though now I look at it, it may just happen as his final power up along with Perfect Susanoo
As you already know Uchiha DNA + Senju DNA = Rinnegan and what not yada yada yada.
Madara is already a prime example of this feat
"Sasuke doesn't have Senju DNA ffs, only a jutsu"
True but you're forgetting one thing, he may not have Senju DNA but someone else does...
It's already known that one Orochimaru takes over a persons body, he gains access to their skills, jutsu pretty much everything overall, thus giving him the power of a Senju. He has already shown great control in using the Zetsus cells to restrain people.
"What does this have to do with Sasuke?"
Orochimaru still claimed to want Sasuke's body, both confirmed by himself and Juugo (this chapter)
By Orochimaru using the Fushi Tensei technique on Sasuke's dying body, the Senju cells would also be transferred thus activating the Rinnegan due to Sasuke's near death experience giving him the final power up.
"How exactly would Sasuke be using the Rinnegan if Orochimaru has taken over?"
From Naruto Wiki: "Apparently if the host of these souls' chakra level falls enough it is possible for them to resurface in material form as seen with Orochimaru surfacing with his own body after Sasuke used up most of his chakra."
Orochimaru has shown to resurface with his body after Sasuke's own chakra levels dropped in the fight against Itachi (only for him to get sealed in 7 seconds.) I believe that the same thing will happen with Orochimaru since his body or soul wouldn't be enough to control the Rinnegan thus causing his chakra levels to decrease greatly allowing Sasuke to resurface somehow and regain control over his body.
"What about Hashirama's technique?"
No clue as to what it could be, though I believe it may be a technique relating to the Rinnegan that either Sasuke or Madara possesses.
As you already know Uchiha DNA + Senju DNA = Rinnegan and what not yada yada yada.
Madara is already a prime example of this feat
"Sasuke doesn't have Senju DNA ffs, only a jutsu"
True but you're forgetting one thing, he may not have Senju DNA but someone else does...
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It's already known that one Orochimaru takes over a persons body, he gains access to their skills, jutsu pretty much everything overall, thus giving him the power of a Senju. He has already shown great control in using the Zetsus cells to restrain people.
"What does this have to do with Sasuke?"
Orochimaru still claimed to want Sasuke's body, both confirmed by himself and Juugo (this chapter)
You must be registered for see images
By Orochimaru using the Fushi Tensei technique on Sasuke's dying body, the Senju cells would also be transferred thus activating the Rinnegan due to Sasuke's near death experience giving him the final power up.
"How exactly would Sasuke be using the Rinnegan if Orochimaru has taken over?"
From Naruto Wiki: "Apparently if the host of these souls' chakra level falls enough it is possible for them to resurface in material form as seen with Orochimaru surfacing with his own body after Sasuke used up most of his chakra."
Orochimaru has shown to resurface with his body after Sasuke's own chakra levels dropped in the fight against Itachi (only for him to get sealed in 7 seconds.) I believe that the same thing will happen with Orochimaru since his body or soul wouldn't be enough to control the Rinnegan thus causing his chakra levels to decrease greatly allowing Sasuke to resurface somehow and regain control over his body.
"What about Hashirama's technique?"
No clue as to what it could be, though I believe it may be a technique relating to the Rinnegan that either Sasuke or Madara possesses.