>>713837442There were later trailers where Snake took Raiden's place, like the Fortune fight, which were Big Shell scenes deliberately made to throw us off.
That's what makes me believe the harrier was legit. The fact that it still takes place in the tanker backdrop and contains elements not include in Raiden's equivalent (like the bridge being invaded with enemies) makes me believe it was always part of Snake's campaign and was simply moved and changed to Raiden's when they cut out one of the planned bosses like Oldboy.