I don't really know... Just basically led Akatsuki by the nose and threatened Obito into making him his co-op in the war?
Also, if he wasn't trapped by Izanami which only actually worked because Itachi was an Edo (will prove if asked, but I'd rather not right now), then it's VERY possible that Madara wouldn't have ended his Edo-Tensei contract, which would have left Kabuto with an uber-powerful summoning.
If he really wanted to own Sasuke and Itachi, he could have just called Madara to where he was and killed his personality before Madara ended the contract.