Tobi is still Uchiha Madara
This is my first post and I haven't done something like this before but I have been thinking alot about who Tobi could be. I know that there are loads of theories but I thought I'd gauge reactions to mine.
I think that Tobi is......Uchiha Madara or at least a part of him.
Madara has the rinnegan and obviously knows how to use it. Tobi knows how to use it too.
Maybe, when Madara got his Rinnegan, he split himself into two beings just as he split the 10 tails into 9 beings. So tobi was created. When this took place is questionable. It had to have taken place after the battle at the Valley of the End.
Madara was eventually killed, maybe because the First Hokage's DNA killed him. Remember that all attempts to combine any DNA with the First's killed the host when Orichimaru did it except for one. Madara may have had rinnegan for a short period of time. That's when he split himself.
Tobi may not have received Sharingan in the split. This is when Tobi and Madara start to plan to change the world. They both decide that once Madara is dead, tobi will take the Rinnegan from Madara and put them in a body that can reawaken them. A body that has loads of chakra (uzumaki) to maintain the rinnegan. This also gives time for Tobi to find sharingan to replace his regular eyes.
Tobi searches for sharingan to replace his own. It makes sense that his sharingan are always on because Kakashi's sharingan is always on. Both eyes are not their own. In the manga he mentions that he got this eye from Obito. This may imply that he replaces his eyes when needed.
When the time is right, he gets the rinnegan back form negatos body. He knows the medical procedure to replace an eye because he has done it so many times before but he does not how to use the Rinnegan as proficiently as Negato. He also needs to keep one Sharingan to complete Izanagi on the world. Once he does so, he will just replace that blind sharingan with the other rinnegan.
The Edo Madara has Rinnegan because he died with them. Tobi's two rinnegan in his possession are from the original Madara body. This would mean that Madara is the only one to awaken the Rinnegan which again makes sense.
Tobi always claims to be Madara but then makes statements like, does it matter who I am. He obviously has some connection to madara based on his extensive knowledge of the history of the Uchiha clan. He also automatically activated the Rinnegan when he put them in his sockets. He didn't use the Rinnegan before because he has a limited chakra reserve.
Also, he has extensive knowledge on how to put the ten tails together again, as if he has already done something similar.
There are holes in this theory, please expose them so that I can convince myself I am wrong, or try to fill in the hole. The wait of finding out is killing me. Thanks.