I had a dream last night he turned into hashi because that's what zetsu can do, only he still had all his ems abilities and the rinnegan. Lol
Your ideas not bad but I'm sticking with he can control Edo's.
WHY?
Because there was a big fuss that hashi broke off oros control and tobirama couldn't.
Well I think this'll come into play. + at the start madara said he knew how Edo tense I worked. (He broke free too)
Madara also seems pretty confident that he can take hashirama and with the speculations that madara knew senjutsu
Is the weakness, keeping hashirama away.. I don't know, that's how I see it.