@Ant
Oars is comparable to Luffy given that Nightmare Luffy should be much stronger than his Gear 3rd mode, but Oars was capable of standing back up from the attacks (while he is a zombie and it allows him to shrug off damage, he can't move if his bones and muscles are destroyed) Zoro and Sanji were each capable of tanking hits from him and dealing some damage, even if mostly superficial.
Kaku has a
Doriki of 2,200 in base while Lucci has 4,000, suggesting that he is more than half as strong as Lucci in base (though this would be suggesting that the average marine is Large Building level). Since Lucci was capable of overpowering Base Luffy easily, he already scales to Low 7-C. Kaku being half as strong as Lucci in base would be At least Multi-City Block level in base, and Small Town level in Giraffe mode since he should be much stronger than base, and he was capable of overpowering Pre Asura Zoro, which should be comparable to Base Luffy.
Sanji was capable of defeating a similarly powerful character, so both him and Zoro should scale to Small Town level in Enies lobby for beating Kaku and Jyabura, and in Thriller Bark for being able to take hits and hurt Oars, who should be comparable to Gear 3rd Luffy via scaling to Nightmare Luffy.
Ryuma would scale from this since he could fight equally with a two-sword style Zoro, making him Low 7-C in tier.
I personally see it making the stats more consistent since all 3 of them together could barely defeat a Pacifista in Saboady arc, while their Post timeskip (Town level) stats could one shot them.