Not really an idea or anything. Just more like speculation on what the One Piece actually is based on recent information in latest chapters of the manga. Well, that and also what i think it is (so yes, an idea,..... weird right? Moving on)
The One Piece is probably an artefact or something powerful left behind by gods.
Its been established already that gods existed or still exist in One Piece world by now. (The human human fruit: Model Nika [Sun God], i think Sengoku's fruit the human human fruit: Model Buddha and probably other human human model fruits are examples of this etc.)
So what if the gods left behind some thing similar to the twin gods of remnant who left 4 relics (creation, destruction, knowledge and choice {always forget this one}) and prolly part of the reason why the world government has been after the gomu gomu no mi fruit now known as hito hito no mi, Model: Nika for 800 years is because only a god or a gods power can access it ("It" in this case being the one piece).
Its a pretty big "what If" but also makes sense (atleast to me). Food for thought.