Good thought but it doesn't explain why people with the Rinnegan can summon it or how it is used as a host for the Juubi.
Madara may have contract sealed that and took it as well as his DNA, and then he linked it to his eyes so Nagato could use it, the Juubi thing I don't know, maybe it needs to have the yang chakra of the sage to be able to control it and supress it, and Hashi was closest in that respect.
Thank you micknerks, the last episode i was wondering and im happy to see it with my own eyes. I equally believe gedo mazo was hashirama's summon to match madara's susanoo. Also, with the sythe that madara was handling in speaking to obito i cant wait to find out how hashirama's possessions found their way into madara's hands.
Hashirama defeated Madara with:
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You stole this from somebody, I don't remember his name. Shame on you..