Board Thread:Naruto Discussions/@comment-30881771-20170815144139/@comment-734582-20170817143844

Ravenlot 27 wrote: Not really, we have a clear evidence that Shin's cloning was happening quite a while before this, since Oro stated that he transplanted Shin's arm to Danzo along with the Sharingans and Hashi's cells within it, meaning it transpired during the times when Oro was still a Konoha shinobi. There is no reference to when the cloning started. We know that arm contains Sharingan and Hashi cells, so cloning wasn't the only experiment on Shin. It's entirely possible that the cloning only happened after Orochimaru's rebirth. Or it could've happened after Orochimaru captured Sasuke, as Orochimaru was hellbent on making Sasuke his vessel and so would not have taken a shin.

Either case would explain in a very reasonable way why he didn't take a Shin.

EDIT: the clones don't look very old, around 12-15 to me, so that would put their birth around the 4th war, give or take a few years. They don't seem to have been aged artificially, as no mention of that is made. So they also would not have been available as vessels around Sasuke's candidacy, and it seems orochimaru was not yet done with his experiments on adult Shin (as evidenced by kabuto's advanced cocktail of powers and the fact that Orochimaru obviously would've wanted such for himself). So, he wouldn't have taken Adult Shin and wouldn't have been able to take baby shin clones as a vessel.