The only good reason for Tobi being Obito would be if Tobi actually wanted to bring peace to the world with his fake war. One can list a dozen of "facts" that he thinks add up to his theory of Tobi being Obito, but all these do not matter if he doesn't find a way to make that reasonable in the plot and make it coherent with Obito's character, as it was meant by the author. And Obito was meant to be a hero, his words are cited by Kakashi in the very beginning of the manga, and as it turns out he defined Kakashi's current view of the world (Similarily to Shisui's influence on Itachi).
So it cannot be that such a hero simply becomes Madara's sidekick in his quest for world domination, or that he wants to dominate the world himself. That would completely ruin Obito's hero status and in exchange it wouldn't give us anything. So i think the only way this could happen would be if Obito's real plan was that such a ninja alliance is created, and as a result world peace is achieved, and then he would accept to die as the "evil" guy (similarily to Itachi who accepted to be blamed for what happened). But even this version is very unlikely, because we see that Tobi's character is quite evil, he does "evil" things that wouldn't be necessary if he was secretly working on such a world peace plan.
Also Madara couldn't have turned Obito like he did with Nagato because there was no hate or anger in Obito when he died, he was happy he could finally become real friend of Kakashi and was happy to save his team members by sacrificing himself, there would be no reason for him to turn against Kakashi. So if we can't find any good reason then it's impossible that he was turned into Tobi.