Board Thread:Naruto Gaiden/@comment-945885-20160421115439/@comment-734582-20160423182254

QuakingStar wrote: He would of got it anyway as he wanted Sasuke's body and to use Hashirama cells on it to grant it the healing ability he desired, that would of gave him Rinnegan. And he probably wanted Sasuke because he thought he needed an actual Uchiha rather than just the eyes (which judging by Shin and Danzo, wasn't working as Orochimaru intended).

Considering Kabuto specifically modified Madara and not people like Itachi, it's safe to say the idea that only very special Uchiha can awaken Rinnegan was pretty high on Orochimaru's list.