We don't know whether or not the Infinite Tsukuyomi is an exception. It could just as easily represent a plot oversight / retcon, or it could be that the person who explained genjutsu at the start was an unreliable narrator. The only thing we have to go on for this argument is the fact that a genjutsu exists that worked on people who did not have chakra, and that genjutsu was not stated anywhere to be particularly "special", other than the fact that it covered a huge area.

Orochimaru doesn't need to control Hashirama. He can just unleash him into the world and explain that Blackbeard's an evil pirate who wants to conquer everything.

Why are you even considering the possibility that he gets different devil fruits? It hasn't happened. There's a decent chance it won't happen. It's totally irrelevant.