@Robby:
Vivi and Carue mark 2. There to lead them into samurai land and get them entangled even more in Kaido.
They're so far off the "potential joining" list I didn't even think of them at this point. Kinemon had some chemistry, but is incredibly dull cut and paste of other character traits… (tall pervy swordsman is pretty matched by Brook already) and Momo had some potential interaction with Luffy in his first chapter, but that fell apart fast. And both of them have fairly straightforward traditional samurai designs.
They are NOT going to cart an 8 year old around indefinitely, and they reeeeally don't need a third swordsman (and they've added a third samurai to the group now on top of it.)
Plus, Jinbe is already joining and filling the "traditional japanese" role. He's a mafioso type and not a samurai, but he'll still be a guy going around in sandals and kimonos.
When we see the next crewmate, we'll know it almost immediately, their design is going to stick out as something Oda spent some real time refining and making unique from everything else in the series.
Bart's design is unique enough he could have been a candidate. And three eyed silent girl under Big Mom is unique as... the only three eyed character in the series thus far (plus Oda took the time to show her off way in advance without much apparent reason)... but as we know absolutely nothing about her, no point in guessing.
I can agree with that reasoning. Kinemon would be a good character to help progress the plot development, but not unique enough to add to the crew. I see Oda trying to round out the talent of the Straw Hat crew with the notable remaining types of characters available. Meaning a logia, a marine, and maybe a mythical zoan. The first and second of my personal list would be satisfied by adding Smoker to the crew. The last would be made true by adding Momo. At least I believe Momo would be considered that. They also would be considered developmental characters who would have the capacity to grow with the crew. That would effectively finalize the crew in my opinion. Then it could be all about the notable allies the Straw Hats add (Law, Cabbage, Chin Jao, Bart, etc.). In reference to your final point, I felt that Momo would be an addition as soon as I saw him. I could see him being taken care of by the Straw Hats as it may be made to seem that he would be safer in their care than in his country.
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@Gizmo:
Kinemon's just suffering from the "Vivi in Drum Kingdom Syndrome". You'll see once the focus switches back to the samurai…:ninja:
I do think it's noteworthy how easily Usopp was able to assimilate Viola's and Kanjuro's abilities for his attack. Luffy's shown to have combos/strategies with other people outside the crew before like in Impel Down or even just this Law fight, but Usopp's attack was the closest I think the other crew members have gotten to fighting alongside others in a way that meshes well. Since Robin is fighting alongside Cavendish and Bartolomeo there might also be opportunities there too.
Just pointing it out here since one of the bigger points I brought up when discussing Kinemon was how fluid it was for him to fight alongside and with the rest of the Strawhats. And even using Usopp as an example of how Oda's showing more examples of the crew fighting alongside other people, I still think the examples with Kinemon show him on a footing that has him with the Strawhats instead of just assisting them or fighting alongside them as an ally for the battle like in the Enies Lobby portion.
That's a good point as well. Kinemon has been depicted consistently alongside the crew in intimate fashion. However, as stated before, that could just be another Vivi type of situation. In Vivi's situation, Oda dropped a bomb on us by having Nico join. Could that be similar to how the story is playing out now. Having a character who in no way appeared to be on the outlook joining the crew and then having their story further developed makes sense again. Momo gets my vote in that regard.