@The:
Why are people assuming One Piece is a big pile of gold
Zephos gonna pop a vein
In One Piece not only gold is Treasure, but that doesn't mean gold isn't Treasure either. I believe One Piece is the treasures gathered during Roger and his crew travels. So I believe it will be Gold and others objects of value for his crew, for him, for the friends they made and maybe even for enemies they fought( Maybe there is something that was important for Garp. His marine scarf or hat for example. And Whitebeard, maybe his hat). Of course, because he probably put his treasure in Raftel, the Ryo Ponegliph and even Raftel now are part of One Piece too.
Probably he had a member who draw all the places they had traveled, so the maps are part of One Piece. He had Crocus that was a great doctor, maybe Crocus wrote books of deceases and cures he found/invented in their travels and his entire life. Maybe he had a cook that stored a lot of fishes/recipes of the places they traveled in the ship and later freed them in a lake in Raftel, The fishes not the recipes. Maybe he had a historian/fantasy writer/Bard that wrote a lot of books with stories and musics about their brave travels and the stories they heard from others. An important thing from his friend Gan Fall and others friends. Even Oro Jackson, his ship, and his hat would make part of One Piece! And last but not least, the countless gold in his crew possession. That would made a Treasure worth of being called the biggest treasure of all, The ONE PIECE!
More, when the Strawhats reach it, they will discover that the possessions and knowledge they gathered through their travels, supplement if not equals(I don't think so, because Luffy is only traveling for a short time, compared with the years Gold D. Roger made has a pirate) the One Piece that they found. Maybe in the end Luffy makes the same thing as Gol D Roger and let's all his, his crew and his friends valued treasures in Raftek. Nami world map or her grapefruit(Mikan) trees(or both), Chopper cures or hat(or both), Robin writes her interpretation of the story, including the void century, Zoro let's his swords(Maybe only kuina) or scarf or the green thing in his belt(or everything), Ussop his tales and songs, Sanji his recipes and some fishes he gathered in the Thousand Sunny, Brook his songs or soul king hat or sword or the dial, with his last song(or everything), Franky the Thousand Sunny, luffy is hat! But it doesn't end here and maybe even something from Vivi, Ace(His devil fruit?), Cobby(glasses?), Kuma(bible?Hat?), Hanckock, Hachi, his father Dragon, Shanks(his sword?), even Blackbeard and Akainu, and others.
That would be a great One Piece!