What if Luffy already has the One Piece?

Think of the iconic straw hat as a crown of some sorts.

I do actually believe that the Straw Hat might have an important significance , might be the crown of the King of the Ancient Kingdom .

As for the One Piece being in ” that place ” , I honestly still can’t understand why everybody in the manga ( and even majority of readers ) assume that he meant Raftel . Roger said nothing about Raftel in his last words .
I believe the straw hat is the key to the one piece because he did actually have lots of treasures he is the pirate king so because Luffy has an advantage and Shanks gave to him believing that he had the best shot of getting the one piece and told him to return it to Shanks when he becomes a great pirate

The concept of Knight in One Piece

Uranus, ancient weapon