This sounds like reasons that you don't want Yamato to join, not reasons that would actually prevent her from joining.
In the first place, why would Oda care about Yamato displacing someone like Brook in popularity?
Shortly after her introduction she made it to the top ten in the recent character popularity poll. She's already far more popular than
most of the Strawhats. Displacing the least popular Strawhats is so weird as a reason for her not to join.
Why would unpopular characters be more likely to join than one of the most popular characters?
On thread:
My only worry regarding Yamato joining is that she may be too strong and threaten the M3 hierarchy (see Jimbe not actually joining until after Sanji got the Raid Suit, it's as if Oda was unwilling to displace Sanji as #3 Strawhat). I'm worried that Yamato would be stronger than Sanji and may remain that way till EOS.
Yamato's Potential:
- She's Kaido's only daughter.
- Kaido taught her his fighting style.
- Kaido sought to make her Shogun (this might indicate that he holds her combat ability in high regard).
Yamato's Portrayal:
- While holding back (and without the use of her DF ability), she could stalemate Ace
- Ace regarded her as strong
- While holding back (and without the use of her DF ability), she could stalemate G2/G3 Luffy
- Luffy regarded her as strong
- Her Devil Fruit seems to be considerably powerful given how spooked Sasaki was at seeing her transform.
I'm not sure how strong current Yamato is, but I would guess that she's at
worst slightly weaker than Jack (given her interactions with Sasaki and Ulti, Yamato appears to be above the Tobi Roppo even without relying on her DF abilities) and at
best slightly stronger than King (there's not much reason to expect her to be on the level of Chapter 1000 Luffy).
Considering her heritage, at EOS, I could see her becoming a Top Tier.
The above could just be my inner Yamato simp speaking.
In expectation, I would place current Yamato above Sanji, and it's hard to see that changing by EOS.o However, Oda coul make Sanji as strong as he desires though, so this isn't that strong a contention.
I'm curious what takes the other Yamato fans on here have.