I think the following characters were completely mismanaged:
- Hiyori: Served no purpose. Not even as fan service.
- Denjiro, Kawamatsu, Ashura Douji: having all 3 were overkill. Oda should had just kept Ashura to illustrate Wano's suffering. Keep one of Denjiro/Kawamatsu if Hiyori is to be kept.
- Yamato: If Oda intended Yamato/Luffy to take down Kaido together, I would've supported it, but the way it ended, he/she did not need to be in the story. I think a better story would've been that Yamato was Oden's daughter and Kaido adopted her and tried to make her his prodigy.
- Orochi's ninja squad (forgot their name) - I could have accepted it if Nami/Robin defeated them in the castle.
- Drake - didn’t do anything. Waste of potential by including him in Wano.
- Toko/Tama - Only one of them should have been included. Both was overkill.
- Ushimaru: Didn’t need to be there at all.
- The Yakuza bosses: No. Even the old man Hyogoro is unnecessary.
- Numbers: Honestly not bothered by them either way. But unnecessary inclusions nonetheless.
- Bepo/Penguin/Sachi - Oda should have left them somewhere else like he did in Dressrosa. Would've been more palatable to know that they weren’t here to begin with.
Inclusions that I liked:
- Yasu: I think he got the point across with Yasu.
- Toko: Having a kid in the story is not bad at all. But making that kid all powerful was stupid. So, even though Tama's storyline was fine, her entrance into the war was bad. Toko on the other hand, got the point across.
- Orochi's Grandparents: Got the point across with them.
Obviously it is easy to say now what worked and what didn’t and Oda definitely didn’t have that option. But I hope Oda looks back at the Wano chapters and finds what he modifications would've worked better.
Regarding Carrot, the question is, is Big Mom down permanently? If she comes back, so will Perospero. And then it makes sense to have Carrot's story continue.