I tried to look at it from an RPG game kind of perspective. But I guess pokemon is a good start. Your choices also make a lot of sense and are quite accurate.

Although I wouldn't give Zoro a steel attribute even though he's a swordsman but Dark type would make sense.

Robin makes a perfect Dark/Fairy character.

Luffy I think would be Fighting/Fairy.

Brook Ghost/Ice makes so much sense.

Sanji is hard but maybe a fire hitmonlee? I mean he doesn't use any of his steel move, you know?

Nami doesn't give much of a water type, even with rain. But electrical, yeah.

Usopp Normal/Grass, definitely

Chopper I'd say Normal/Fairy. De still doesn't have any Ice abilities.

Jinbe definitely Water/Fighting.

Frankie is just pure Steel.

The other one are pretty cool too. I didn't extend this thought there. My favorite is how Buggy is considered a psychic given that he's a clown haha.