@Airflow:
It's obviously a complete history of the Void Century but I don't think that would be enough to bring down the World Government by itself. The things they did back then happened over 700 years in the past, it's hardly relevant to the World Government of today. No matter how horrendous something is, if it's done that long ago then it's quite easy to forgive. Plus we have no idea hat actually happened, I personally think they genocided the Ancient Kingdom but even that might be justifiable to some (Akainu and his ilk) if they claim they did it to protect the world from the Ancient Weapons. I just don't think the history alone can bring down the World Government. But then again, I don't know what could. I think it'll be something that Robin reads in the Rio Poneglyph and then Luffy can act upon that information. And his choice itself will be One Piece, the choice to choose the future of the Grand Line, between freedom/chaos and order/repression. Between positive and negative freedom.
I don't think of it as a sort of "i win" button against the World Government either; it'd be more the catalyst for making major changes to the way things have been going in One Piece since I don't see them actually being taken down. The World Government likely has always and still does have the best intentions which probably back during when it was first established worked well. Then over time leading to the present they've strayed from the ideals that their organization was built on in their paranoia but overall they've done good.
The average person I'm betting doesn't join organizations like them and the Navy to oppress people and are in on things like the Void Century. Things aren't so cut and dry, which is probably why Rayleigh said what he said to Robin back at Sabaody.
Me personally I've always thought the World Government acted so decisively during and after the Void Century because whatever went on then was utterly horrific and dangerous. Pirates having complete rule over the oceans, citizens lives being spent in constant fear, basically the Cocoyashi Village scenario everywhere. Plus there were the Ancient Weapons and the carnage they caused. I'm guessing the 20 kingdoms united together and fought a complete annihilation campaign against the Ancient Kingdom until all of it's citizens and most of it's history was gone and some order was retained. The WG, fearing this chaos would return, implemented brutal measures to ensure order like Impel Down. Any kind of detractors asking for more freedom (Fishmen) were sold into slavery to discourage any kind of rebellion. Over the years this may have been slightly phased out because order and prosperity was slowly returning (like when slavery was "abolished") but the underlying intent remains.
It might have been that way yeah, and I personally would lean towards what you've written above. The ancient kingdom may have been even worse than how the World Government are currently running things, and back then they were fully justified in taking them down and bringing about the inception of these 20 kingdoms coming together. The problem now is that in the World Government's fear-induced paranoia of the "Will of D." they're creating the very people who are dead set on toppling them, like Dragon and his revolutionary army.
Basically the World Government is freaking out over a threat which doesn't even exist anymore(except maybe Dragon), and genuine good change can't happen until things move past this.
Also personal theory: The Elder Stars have remained alive for over 700 years via Bonney's fruit to ensure order has been maintained. But this could be a load of crap.
I think it's more that the Gorousei finally discovered whatever Devil Fruit to become an age(wo)man, but Bonney had already eaten it and they don't want to risk losing out on staying alive indefinitely since who knows where it'd pop up.
Since from what we were shown with the Ushi Fruit: Model Giraffe and the Awa Fruit, I doubt every single Devil Fruit has been discovered and subsequently catalogued in the encyclopedia.
Here's the point where you've got to examine the issue as Roger himself didn't do anything with the information. Instead he encouraged others to journey their by claiming he hid his "treasure" there. But honestly I don't think Roger would find "information" to be a treasure in the same way Luffy wouldn't consider it to be treasure. Again, this sounds like Robin's dream.
It's really about going through the journey through the Grand Line and coming up with one's own answer once they make it to Raftel. The conclusion Luffy may come to with the information might not be the same as Roger despite whatever similarities they may have.
The Strawhats may not even care about changing things, but it will happen nonetheless with them at the source since it's just the kind of story One Piece is.
Sorry this is a bit of a ramble, I find it hard to convey my thoughts coherently on this matter because so much of it's completely unknown and I guess I haven't really reached a full conclusion yet.
It's fine I think I understood what you were getting at. Correct me if I'm wrong anywhere though.