Right, I just don't understand why you think that third coffin was Madara. Your theory could work without that. Obito didn't like Kabuto resurrecting Madara, but he didn't think there was some further plot to it. What Im wondering is why would he think Oro had some other plan just by knowing he was going to use Madara against the Third? If that makes sense. Basically, why kill Kabuto if he knew Oro was trying to summon Madara when Kabuto ended up summoning Madara anyway.
Also, another thing that gives me problems with this theory is Oro still wants Sasuke body. I think, and this could be way out of left field, but if you're theory holds true then I think you need Sharingan to stop or be immune to infinite tsukyomi, hence why Obito killed them all.