I reaallly reeaallly like this theory! Many thumbs up for this Typhon :worshippy:
Only thing is that it don't actually have to be Obito's full body that Tobi is using. Especially because his face looks old. But his Sharingan, I'm almost sure too!
For the people who haven't read my theory yet, I'll repost it under this message. To show it to more people, and to keep the little credit to myself

I already see a few copies.
Thanks for the reactions so far btw! And again Typhon, I really enjoyed yours! I was lucky to read the original one, before is somehow disappeared..
And now my theory about Tobi:
1.Old Face, about same age as Danzou
2.Was in a team with Danzou during the Ninja War
--> explains why he wasn't surprised by any of Danzou's techniques
3.The team they where in was Tobirama's team..
TOBIrama
--> Tobirama was the first Shinobi with space time Jutsu
--> Explains why Tobi could use S/T-jutsu without MS
4.The only two of Tobirama's former team not present at Demon Fox's attack --> D & T
--> see
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and than look at
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to see that they are clearly missing
5.The only two characters besides Yamato with Hashirama's cells --> Danzou & Tobi
6.The only two characters with a massive collection of Sharingan --> D & T
7.Both contributed to the Uchiha Massacre
8.Danzou never acted surprised about Tobi either, as if he knew who he was
They probably where close friends before, with the Uchiha massacre as a part of a plan and vision they shared. But it seems along the way, Danzou had more interest in becoming Hokage and Tobi (Kagami!) in bringing the whole world under his control.
I think while they didn't agree, they decided to just split up without a fight, because they where comrads once.