This topic started 4 years ago. Developments that have happened during these 4 years have pretty much rendered his argument invalid.
It is too improbable that the Rio Poneglyph is One Piece. That would mean the world's greatest treasure only applies to Historians. Other people's dreams of becoming the world's greatest swordsman, all blue, etc… would be rendered moot.
True, you could argue that the Rio Poneglyph is the key to the World Government's topple. But as of now, we've seen Whitebeard alone very nearly wiping out their main fighting force - the marines AND the Shichibukai. The feat of "toppling the World Government" could be safely be assumed to be attainable by two YonKou working together. For example, if this current war was BOTH Whitebeard and Shanks vs the Marines and the Shichibukai, I'm sure the Pirates would have won. Would this not then render the finding of One Piece (which in OP's opinion is the Rio Poneglyph) moot?
Oh, but we also have the ancient civilisation! That's... exactly what they are. Ancient and wiped out. How could the One Piece treasure, sought after by all the world, be about studying a civilisation that no longer exists? I simply don't see someone like Blackbeard caring about such a thing.
That leaves, "The Will of D" as confirmed by Nico Robin and Rayleigh to exist. That is the last thing remaining that gives OP's argument any merit. "What is the Will of D.?" Rayleigh has confirmed it's answer to be a result of maturity and understanding over time spent on the journey through Grand Line. And the answer could be elusive, people may reach different answers. The Rio Poneglyph in this case would be only a key to the understanding of the Will of D.
My guess is that One Piece encompasses something much larger than the Rio Poneglyph, and hasn't been introduced to us yet. The Rio Poneglyph itself is probably a big factor in the One Piece treasure, but One Piece is MORE than just a wall of text.
Besides, now we know that Roger could be referring his "treasure" to be Ace and Rouge. "That place" was only implied to be the Grand Line, it coulda been Baterilla Island in South Blue for all we know, couldn't it? In all this theorycrafting, such an argument would pretty much hold the same merit as OP's argument!