I forgot all about Jinbei. xD
Yeah, I seem to have been swept away by the highlighting of his crew position in the most recent chapter and it slipped my mind that Jinbei has actually showcased strategic planning in the past. I'll concede that to you.
However, I will contend this point. Positions aside, I don't agree with this line of thinking. That Luffy didn't know Usopp and Chopper had their respective positions doesn't matter because the story itself called for those positions (err… well, except for Usopp; though his position has definitely come in handy). This would be one of those situations where what occurs in-story amongst the characters is irrelevant when we, as the readers, understand the necessity of the positions and the expectations that they will be filled. And while it's true that Oda could introduce anything he wanted in the literal sense, we have 20+ years of precedent to go by. "Because it's Oda" isn't an argument. Not when we have easily discernible story structure here.
No disrespect, of course. I'm only really contending this because I'm expecting stronger points from you. I could concede that you're reaching the right conclusions for the wrong reasons.~
The design would be the tell tale sure, but if we could deduce the position then we could potentially also deduce other important factors such as crew dynamics and story implications. It's really all we have to go on right now since Jinbe is 100% solidified and, so far as I can tell, there are no currently viable candidates.
We can almost never deduce the position though. Unless it's a recurring gag like Luffy wanting a musician, the relevance of roles like cook, doctor, and shipwright only come up when we are about to enter the arcs where those crewmates are introduced. Even though there was buildup for the shipwright in the ship getting wrecked throughout the series, nobody seriously considered that we needed an official "ship fixer" to join when Usopp seemed to be doing a tolerable job. It's nearly impossible to deduce what position could be needed, especially this point in the game. And even if we could, there is absolutely no way we can use that as a gauge for what kind of new character could join the crew. The most you could ever do is see if an already established character can fit such a role.
Which means… we agree. So I suppose what I am saying that if we agree that there are currently no viable crewmates, then there is almost no way to tell what or who the future crewmate will be by pitching crew positions with how many have been filled up. We only ever understand the necessity of crewmate positions when it's brought up. I think that any hope of knowing what role a future crewmate would "need" to fulfill before that role got diegetic focus went out the window when Chopper joined as the doctor. Navigator, cook, and doctor are the only roles I could see people intuitively predicting ahead of time without story emphasis since those are all basic positions you need for long term ocean travel.
I'm sorry to disappoint you with such an answer. We can predict a lot of things in One Piece due to how formulaic and trope-y it can be, as well as how far ahead Oda plans his plotlines. But with things like crew positions, I think it's a lost cause to think hard about it.
Who knows? Also, the completion of the core crew is going to be a pretty big deal in my opinion. This is something Oda will have been waiting to do for 20+ years and won't just be carelessly passed over. Having something like officializing Zoro as the Vice Captain could be a nice way to round out the experience of building the crew through the years although admittedly it could be something else. In either case, it'll be something special.
But why would it be a big enough deal to promote a crewmate? What would such a decision have anything to do with the consensus that Luffy's crew is complete? This isn't even something Oda would need to wait 20+ years to do, he could have done it all the way back in Chapter 3 when Luffy first met Zoro. I would think that if you want to establish a character being your protagonist's right hand man as an official title, you would have that happen as soon as they decide to venture together. Or at most in the first half of the series.
You're missing the point. I don't think each Straw Hat will fight their Blackbeard counterpart by occupation either but there's potentially something very special about the final member of the crew, maybe even something special to the point where we're not even allowed to see them yet since even by virtue of seeing them it would give away what their position is, and thus what their story relevance would be too. Even just that intrigue could give us insights into who this last person could potentially be since it indicates it has to be something bigger than the garden variety tag-alongs like what we see with Carrot.
Or, he just hasn't revealed the last Blackbeard because he hasn't gotten a chance to yet. =P
It's still interesting to postulate on why that might be.
Edit: Whoopsie. I think I may have talked myself into agreeing with you there. Regardless, my question is, "Will it be precedent or something brand new that we should be expecting?" The forum tends to favor precedent but the final crew member might be a special case so which basis do you side with?
Not rhetorical btw, I'm genuinely curious.
I can agree that there might be something special about these final members that are keeping them under wraps simultaneously. I actually hope there is so that they have interesting chemistry. Or Oda just hasn't had the chance. Both are very likely. Especially when we haven't even seen post-timeskip Teach yet, but that is probably because Oda has a special big entrance planned for his debut with a fully-grown braided beard.
The forum would only favor precedent out of convenience for theorizing and general desires. Oda's quirky and he will make whatever he wants work. I know that sounds like a vague "because Oda" answer, but consider this.
That image is from One Piece Data Book Green. And if I am correct and not having a faulty memory as usual, one of the scrapped characters on the left (probably the creepy bandana head one) was supposed to be a botanist. That botanist profession probably got swapped to Usopp. Would you think that a botanist is typical to have for a pirate crew? Not really. But it can fit a surreal pirate adventure. Montblanc Noland was both a captain and a botanist, which allowed him to know about plant species and poisons/illnesses.
If Oda wanted both an archaeologist and botanist, the range for what kind of crewmate positions he can want is quite large with such an imagination, to say the least.