If Oda turned a literal gag like "instant digestion" into an actual canonical technique where focus alters material conditions, then Big Mom's weight, fluctuating based on her mental state, fits perfectly..
Exactly. Since this is kind of a worldbuilding baseline that one would come up to at the very beginning of the worldbuilding process, we could push that idea very far, for example, the apparition of Merry, could be a consequences of the intersection of the strongest element in the verse around that idea that will can shape reality (Gear 5) and this basic universal law. If it's the case, then only ships on which a user of the Hito Hito no Mi model Nika can become sentient. This would explain why the klauberterman became a legend but was never seen and it would also indicate that JoyBoy might have had a sentient ship as well.
do you think permanent environmental changes on islands like Punk Hazard
Perhaps, it's a possibility, but in this particular case I would rather call it a physical byproduct of a enormous battle. Aikainu and Aokiji probably fought all around the island, creating massive elemental shift, perhaps the nature started to pick on that and change progressively physically or perhaps the environment was influence by their will, I don't really know.
But there is room to think that awakening is indeed a form of intersection between the will of the user and this basic universal law.
Of course, this is only speculative. The idea of changing the environment with the will is a natural derivative of fantasy so it's only natural that One Piece pushed that idea a little further, it doesn't mean Oda created a specific universal room like that. I approach worldbuilding with a rather physicalist mindset usually, but I know that Oda is a lot more loose with his principles.
For now, I would say it's 50/50. It would explain almost everything
(things like the influence of socialization or more physically the weight of memory proves that Oda can go deep into the physicalist and materialist approach to rationnalize his world), but it's so good at explaining everything that perhaps we ought to see it more as a logical consequence of the fantasy and comical/adventure genre pushed to the romanticization limit.
On my part, I like the idea of a strictly ruled worldbuilding at the beginning of the story that kind of shift toward a more looser and universal approach toward the end. This represents that sometimes magic and reality kind blur. If we look at our universe, there are some occurences where the clear cut physical rules on a specific physical scale (like the universal scale) are much blurrier when we look at the universe in a different scale (like the quantum scale). In One Piece, this could be approached in a way as if all the magic system, the haki, the devil fruits, the awakening and phenomenon are in fact the consequences of simpler and more universal universal rules that shift around on a form of what we could call "wavelenght".
And if everything is connected, perhaps Gear 5 can tap into all these power at once and create something new.
