I dunno, it looks like you're trying to absolve Gast from something he most probably knew about.
-It's his project, so how could Project S and Project G slip under his nose? If he didn't authorize it, how could they become official Shinra ongoing projects? How could that happen if he DIDN'T authorize it? He sounds like a shitty scientist who never got anything done if what you say is correct.
-It's more likely that the MYSTERY THIRD SCIENTIST is Gast, who we know is connected to the project, than MYSTERY THIRD SCIENTIST.
-The Jenova Project's purpose was to produce humans that had the powers of Ancients. Gast was the head of that. He knew that. So even if he somehow DIDN'T know about Project S or Project G (which is dumb, because that's not how scientific research works, scientists have to report their findings and progress to their superiors and ultimately the organization they work for), he DID go into the project willing to experiment on humans somewhere down the line.
-Alright, according to you, Gast probably didn't know about Project S or G, but Hojo, Lucrecia, and Hollander just skipped Gast and reported their findings to Shinra directly or something and Gast didn't know about it? Is Gast retarded?