Oda doesn't have a checklist for crewmembers, I'm sorry thats just straight facts. His relationship to One Piece is too deeply emotional/personal for him to view new members in a cold logical way.
All nakama theories that don't take that into account, is missing the forest for the trees so to speak. The reason everyone's nakama theories devolve into hyper-specific requirements is because Oda doesn't have a pattern other than "I want to add another crewmate" and "The next crewmate has to be memorable". We've yet to see a "standard" manner of joining the Straw Hats and it's kind of silly to think we can figure out Oda's secret Nakama equation (that he most certainly doesn't have). By the end of the series we're going to have 50 different "rules" for new nakama that Oda NEVER used in his decision making process.
A new Straw Hat won't be a boring character, they will have some sort of bond to the SHs, and they'll have focus in their arc thats guaranteed. But the overarching narrative, the crews needs, and the characters motivations in general are the real indicators for a crew join at this late of a stage.
Which is why Kizaru will join the crew once he betrays the WG and has no choice but to scamper off with the Straw Hats. In this essay i will....
The biggest requirement will always be having a dream that involves sailing around the world.
Luffy wants to find the One Piece, so, he has to sail around the world.
Zoro wants to become the world's strongest swordsmen, so, he needed to leap out of the well he was in and go from a frog to a dragon
Nami wants to chart the entire world
Usopp wants to sail as a brave warrior of the seas
Sanji wants to find the All Blue, a mythical sea
Chopper wants to research medicine to be able to cure anyone and any disease
Robin wants to find the Rio Poneglyph and true history
Franky wants his ship the Sunny to sail around the entire world
Brook wants to go back around the world to see Laboon again
Jinbei wants to free Fishman Island, which requires the final war to defeat the Celestial Dragons, which requires the Straw Hats finding the One Piece
This is why most modern candidates didn't make sense, besides Carrot.
Kinemon and Momo, despite getting invites, need to rebuild Wano (Vivi parallel); their dream was to defeat Kaido.
Bonney's dream is now to avenge Kuma and destroy the World Government for enslaving him. This fits more with the Revs than the Straw Hats, since the Revs view the Gorosei as actual enemies.
Yamato's dream was to fulfill Oden's Will/go out to see, so she's stuck in Wano until Pluton is activated and the borders open, at which point she can go out to sea.
Carrot wanted to fulfill Pedro's Will, which was to bring about the Dawn, when Pedro wanted to sail with Roger. Since the Straw Hats are the ones who will bring about the Dawn, Carrot should sail with them, she needs to take care of Zou and rebuild it, like Momo and Vivi before them.
Tama's dream is to become an enchanting kunoichi, and sail with Ace, and now Luffy. She needs to learn Ninjitsu, and become older; so, probably a Shinobu age up if Tama's going to join, like with Momo.
Vivi's dreams were to protect her country Alabasta and sail with the Straw Hats. Now that she can no longer return to Alabasta as the World Government wants to kidnap/imprison her, Vivi is free to join the Straw Hats, and will show up in Chapter 1003, 1000 chapters after her debut in 103.
Lucci so far has no real basis to join the crew, since he has no dreams that we no one, and just wants to murder people. Until we see the flashback detailing what happened to CP9 in order to allow them to become CP0. Oda is clearly holding something back regarding Lucci.
Since CP0 reports directly to the Gorosei, and Lucci has failed to complete his assignment, when Zoro beats Lucci, I expect Saturn to give us some update on him, or have him state something that makes Lucci remember the time skip.
Since Vegapunk's goal is to give free energy to mankind, it's possible he or a Satellite joins the crew to search for ancient technology on Laugh Tale.