This stood out to me. I don't follow. Would you care to elaborate?
Well, I'd have to compile a lot of stuff in order to make it coherent, so I'll just focus on one or two more recent arguments, and if those spark your interest, I'll make something more elaborate:
What have we learned about Brook since his introduction? He knew quite a lot about the deep sea, when the crew was travelling to Fishman Island, despite being found in the first half of the Grand Line, and he knew the Germa Empire. That's pretty much it, and he was a character that Oda had sketched/thought about since before Alabasta started. He was also the commander of an assault convey on a "certain kingdom", and I seriously doubt we have a lot of new kingdoms left to visit, so it's going to tie into an ongoing plot point.
Wano picked up on a lot of stuff from Thriller Bark, and while it was obviously supposed to give Zoro his spotlight, not Brook, it was also the arc where Brook got introduced, so Oda usually makes some sort of association. He barely did anything the whole arc, but we did have some interesting metaphors that might've gone unnoticed: Kanjuro and Apoo.
Kanjuro was the traitorous artist hiding his abilities, with a weird hairstyle, who we had been following since Dressrosa, and during Oden's flashback we were told that he was a weirdo that was found stealing hair from corpses to make brushes, while having secretly been given a devil fruit to help the Kurozumi coup come to fruition. Brook was found on a sea of corpses, has mentioned the importance of his hair, and his Devil Fruit has a lot of potential.
Apoo was the traitorous artist, with music related powers, that commanded the failed Ancient Giants, a plot point that's been around since Punk Hazard. He was also a member of the long armed tribe, and Brook coincidentally stayed with them for part of the timeskip.
We also have Aokiji, that shares a physical resemblance and matching devil fruit themes, and he's either a spy or a traitor.
We got introduced to Rocks during this period, and they're from around the same generation, something that very few characters have in common.
If you find these arguments compelling, I could go on, but I think it's these ones are a good starting point.