"ROGER’S DREAM"
The Golden Pattern (starting from here everything is 100% theory)
MEN’S DREAM
Roger’s will that Whitebeard was talking about, it actually wasn’t his original will. Roger inherited it as well from waaay back then, from 800 years ago to be precised. Yes, it was originally the will of The Ancient Kingdom (let’s call it AK from now on).
The AK was a big kingdom, it ruled over almost the whole world (just like WG does now). They apparently also had a pretty-advanced civilization. One could say that there’s almost nothing they couldn’t achieve with everthing they got at the time.
However they had an issue. As we know, the planet of OP contains of big four seas, east, west, north, and south, each were separated by the Red Line and the Grand Line. The AK saw Red Line and Grand Line as a big obstacle because they have been been preventing people from traveling from one sea to another, thus preventing the AK from reaching its full prosperity as well.
And So they made this project, an insane one, but has to be done. The project was about eliminating the Red Line and Grand Line to fuse the 4 seas into one big ocean, the united ocean. The called it the project of “One Piece”. In order to do so, they started to build some weapons which will be strong enough to destroy the red line (later called Ancient Weapons)
It turned out that not everybody was pleased by this project.. you know, politics. Some other kingdoms were totally against it, they smell a conspiracy was playing behind it. But the AK stood their ground no matter what. Guess what happened next? a huge war broke out. It’s the AK vs 20 kingdoms who were against the prject of "One Piece”.
The 20 kingdoms came out as the victor and they declared themselves as The World Government. Meanwhile the AK was reduced to shred, along with all their historiy, and the “One Piece” project was never heard again since then.
THE FLOW OF TIME
Unexpectedly, The AK has anticipated their downfall. Before the war begun they had carved historical notes on these certain metals which as hard as diamond(later called the poneglyphs) and hid them throughout the world, along with the weapons they’ve built. The AK really wanted to make sure that their desire wouldn’t die in case of anything bad happened to them.
the WG was mad with this fact and completetely prohibit any form of poneglyph dechipering.
but it's too late, the will has been passing through ages since then… silently waiting for someone to recieve the massage.
THE INHERITED WILL
800 years has passed, a pirate named Roger sucessfully reach Raftel and discovered the true history. He knows exactly what to do, but unfortunately his body didn’t allow him to… he had this incurable disease, remember? whereas the project needs a lot of power and time to complete, 2 things that Roger didn’t have that time.
Therefore, he decided to create The Golden Age of Piracy instead, hoping that there will appear someone who is strong and righteous enough to complete the massage in his place.
Who will be that ‘someone’? I think we all know the answer. :D