I think that Oro wants Sasuke's body. Kinda like the grass nins body he had in the Forest of Death, except a perminant deal. He'd be a lot stronger with Sasuke's body, and he'd be able to take out Itachi probably. Oro would be able to get stronger very quickly, because he would know how to use the chakra of Sasuke's body to its potential. During the episode in the preliminaries when he confronted Kakashi, Oro said Kakashi was lucky because he already had "it." Above all Oro wants the Sharigan. He doesn't need Sasuke as a new right hand man, Kabuto will remain in that position unless he kills Oro.