@BattleFranky69:
I can kind of get on board with that, in the sense that Zoro and Usopp weren't exactly essential, they just had fun personalities, but regardless of having what would be considered a vital role on a functioning crew, their abilities have long since become indispensable.
For what I mean of "essential role", I really recommend the link I posted before. It's a really short video, so you won't lose much of your time. As I said, I'm not talking about the job inside the crew, but how these characters rounded up the plot and complimented the guiding light of this story, that is, Luffy.
And that's why these are the Strawhats that will be the emotional center of anything of relevance to the crew outside of their own arcs. For example, Sanji went missing after being captured by Capone in Zou? Then the ones arguing about what to do are Nami and Zoro, not Brooke and Robin. Sanji is beating the crap out of Luffy? Then Nami is there to witness, not Chopper.
That's never how Franky has felt, are you kidding? I mean, he is my fave character so I'm admittedly biased, but he designed and built (with help) the Sunny and all the accoutrements that have since come with it, not to mention duplicating Vegapunk's laser tech and upgrading his own body to the nth degree. You can get away with saying Brook's not so greatly needed, but then a musician is more of an aesthetic preference for a crewmate, not really altogether essential, so in his case, it's both fair and true to say it for him, but not Franky. Especially now with the Sunny potentially totalled. That said, it is true that another 'Brook' wouldn't be that essential and would probably fall to the wayside. Fortunately my next-favorite, Jimbei, is awesome as hell and doesn't seem to be having that issue either. Point being, we ought to want the next character to leave us in no doubt that they'd be able to avoid that, and Carrot just doesn't. Not her fault, of course, but that doesn't change things.
What I mean by "essential" is also relevant to answer this question. I'll give you that Franky's got revelancy because of the symbolism of a ship for a pirate crew, but his existence in the different adventures of the crew is not essential. He's a deluxe background character that sometimes gets a highlight that is parallel to the meat of the plot. Technology and stuff are nice ornaments, they're aesthetics (as you said for Brooke), but they're not themes in One Pieces.
Maybe I'll change my mind depending on what Oda does with Sunny after chapter 900.
And I completely agree, but if he's grooming her for being that, he's doing a poor job of it and I don't want to have to wait to be jonesing for someone to join after they're introduced. There's got to be that spark, that thing that makes me want them to stay, and she hasn't been given that opportunity. If she did, I'd have expected to have already seen it by now. Him dragging it out, if he's going to pull a fast one on us, is not endearing. It'll just make it harder to be cool with it down the line. Get on with it or don't bother, essentially, is what Oda should do. Tick-tock.
But that spark is very personal. I'd say she got special attention from a lot of reader in her introduction, so much that people felt it was weird when she became secondary to Wanda in Zou. Anyway, I have an older post about what Oda may be doing with Carrot's development.
Gonna dispute the development part but I can at least understand why some feel it's been given enough. Also while she 'fits' the crew, those features are already covered by existing nakama and that's why it's so hard to give her credit for that, especially when 'Bropper', the one she's most similar to, is right there in the mix with her to constantly remind us of that.
Carrot seals the deal. She's got enough individuality and enough of the collective vibe. And I think she's closer to Luffy's personality than Chopper's.