There are 3 candidates that want to go out to sea and adventure:
Tama
She had a connection with Ace and wanted to leave with him but due to circumstances was restricted at the time
Yamao
She had a connection with Ace and wanted to leave with him but due to circumstances was restricted at the time
Carrot
Has been travelling with the straw hats ever since she met them, right up until current time.
If people are saying Yamao is going to join the crew just because she wants to adventure, then they have to keep the same passion towards Tama and Carrot. Characters who also have their own promises and desires to set out to sea.
Yamao and Tama merely
wish to set out to sea with the straw hats...that's something Carrot is already actively doing. It's not like she needed to join the straw hats when she did. She would've been in Wano arc regardless of if she came to WCI or not. So why did Oda do it? That's one of the things that separates Carrot from the other two. She has a history with the crew on the sunny.
But what also divides them is the new bonds Oda is developing for the characters. Mainly Tama and Yamao with Momo. And how Oda is presenting Yamao in the role of his guardian, whilst dropping hints for Tama to do the same.
That's not to say that Momo is their only bond. Tama is obviously close with the straw hats and means a lot to Luffy. But when looking in the future based on what we have there is nothing indicating a continued relationship with Luffy post Wano, whereas Tama's already introduced the idea of watching over Momo as a kunoichi. Likewise, all of Yamao's declarations of travelling at sea were before she knew Momo and the scabbards were all still alive. That's a huge deal since she now believes Momo's going to be the one to bring in the dawn and states just how important he is and that she would give her life for him.
And no, this isn't forced labour, or stripping Yamao of her freedom. This is exactly what she wants to do more than anything and is the fulfilment of a wish she thought she'd failed at decades ago. These are her most recent feelings and show that she values the protection of Momo over her desire to go out to sea.
Still, the fact that Oda mentioned this wish again makes it seem fair that she gets to eventually do so. And since Tama wants to do the same thing it brings in to question Momo's role on Wano. After the war, I envisioned the beginning of the preparation for the war against the WG. Wano would be the allies HQ (natural fortress and all), and Momo would stay there. But now I wonder if Momo will be the one to go out to nations sympathetic with the beliefs of the AK and to ask for their help and recruit them to battle. This would achieve multiple things.
1. A perfect opportunity to demonstrate Momo's maturity, strength and worth as a shogun by travelling across the world to recruit allies
2. By choosing Yamao (daughter of Kaido) act as his escort and guardian it would remedy the Wano citizens' mistake of blaming children for their fathers' sins
3. Allows Yamao to simultaneously see the world as they go to each island to recruit, protect Momo, aid in bringing the dawn. (The same goes for Tama, especially if the theory of her being a Kurozumi is true)
There are many ways to travel at sea. You don't have to be on the Sunny to do so. But unlike the suggestions for Carrot, Yamao has shown a very strong interest in protecting Momo. She's strong enough to travel the new world without needing the SHP. She has a log of Oden's travels and knowledge on what the D is (Which would be useful in recruiting AK allies). Meanwhile Carrot's already begun her adventure with the straw hats and has bonded with them to the point that she just feels like another member in their family.
Why take Carrot away from the straw hats and put her on different adventure despite already having travelled with them for over a month, whilst simultaneously taking Yamao away from Momo and grouping her with the crew where she has no purpose for being?
