"I also want to recompose the structure of the final saga to close it as fast as possible~"
Honestly to me, this reads like he's just trying to consolidate and better order storylines. I think people take this language and automatically assume he's going to rush his story.
Hell, it might actually be better in the long run with tight pacing. Imagine he cuts the tertiary "tama-like" characters from remaining arcs? Fewer side characters in Elbaf? Plotlines where he gets right to the issue and resolution within 50-60 chapters instead of 100?
I'd argue that this is ultimately the best for the series, if this is the intent. I personally doubt it's about h8m cutting actual ideas though. Remember, he didn't cut Green Bit and Dwarves, he added it to Dressrosa when it was meant to be a completely separate arc.
Another example I can see of this coming (and have guessed for a while) is him combining Elbaf plotlines and adventure with Vegapunk and Kuma. Idk, just something to think about