Some people here and there on the internet have made a numerical/mathematical approach of predicting the last Straw hat member, seeing as Oda likes to work with those things in his manga as well (Source:
https://www.crunchyroll.com/de/anim...-used-math-to-guess-the-next-straw-hat-pirate ). Up until now every Devil fruit-user on the Sunny has eaten a fruit that corresponded/sounds with/like two Japanese numbers from 1-10 (You are not able to do that with most other DF-names of other users – I have tried it. And the possibility of all DF-user of the Straw hats being able to do that with their DF-name is just too low to be a coincidence.):
Luffi: Gomu – 5 and 6
Robin: Hana – 8 and 7
Chopper: Hito – 1 and 10
Brook: Yomu – 4 and 3
That leaves 2 and 9.
With his Neko neko no mi Lucci comes very close to ni = 2 and Ko = 9. The difference is the `e´ in the `ne´ in contrast to `ni´. However, what many people do not know is that the `ni´ sound of the numer 2 is pronounced `ne´ in Japanese. That means the actual pronunciation of 2 and 9 together is `ne-ko´. So, there we go with the numerical approach – fits like a glove… .
Also, if Lucci joins the Straw hats and Kuzan joins Blackbeard, then we have two ex-WG-members, who are going to face off, when the Blackbeard and Straw hat pirates finally clash. Fits as well.
However, I have a slight change to make in my prediction.
As Shaka and Lucci are mirroring each other (- and they are doing so in many ways – I already explained), and if Shaka represents `good´. Then this means that his name, referring to Budda Shaka-Nyorai (Japanese religion), also needs to be reflected in the other as its counterpart. And again – it fits perfectly – because what religious creature of the bad kind bears a similarity to the CP0 agent’s name? That’s right - `Lucci´ as a short form for `Lucifer´. It also fits perfectly with the demon-theme of the Straw hat crew that everyone talks about. Additionally: Cats are seen as creatures of the devil since the "Hammer of Witches" came out during the darkest phase of the middle ages.
And again Lucci is not bad or a sadist – he is just cold. Anyone referring to him as such is not diving into character analysation deep enough. – just read my evaluation of his character here (-rather far down in my first post and above the side notes. Start about after 2/3 of the post):
https://worstgen.alwaysdata.net/forum/threads/what-will-further-happen-on-egghead-–-give-me-your-theories.35873/post-3760302