Re: Why did Orochimaru consider Sasuke's body as the "perfect body" for himself?
When Orochimaru went for Itachi - going by the early formation of Akatsuki and the timeline - Sasuke was around either 7 or 8, hence the only possible solution was to gain Itachi's body. Had he known that Iatchi was suffering from a festering illness, I doubt he would even have been his first choice. Regardless, Sasuke seems to have a very powerful chakra - more sinister than Madara according to Kurama - a healthy powerful body, and sharingen. This was a perfect combination for Orochimaru to the Rinnegan. As only an Uchiha with an EMS can unlock a rinnegan through the DNA implantation.
Sasuke presented a great opportunity for Orochimaru to gain the command over the 7 paths. It's only logical for him to choose a Shinobi who would prove to be an assect as a vessel, rather than a hindrance. I hope this explained it.