I disagree with idea of characters being finished.
Yeah I agree with you, many characters had their arc story end, but still...
1. Riku story Arc ended in DDD but doesn’t mean we should get rid of him
2. Sora definitely not going anywhere since his the main protagonist
3. Kairi Importance felt like it ended in KH1/KH2 but now she is Finally getting to explore her past I say her story arc didn’t finish yet
4. Roxas Story Arc seemingly ended in kh2 when he accepted that he was a nobody and also accepted to be reunited with his other Half “Sora” but luckily was given the opportunity to be saved and be his own person, now Roxas is back and I can say his arc has been concluded, he can still stay and be given a new role, you know characters can get new roles they don’t have to be written off
5. Xion same situation as roxas
6. Axel story Arc involved his old friend Saix and his best friends Roxas and Xion, his arc of saving his best friends Roxas and Xion was achieved but his role is not over yet seeing as he and Saix still need to track subject X
7. Terra Story arc is sad cause Terra wants to redeem himself after all the problems he caused, his story arc feels like it only began
8. Aqua story arc revolves around her wanting to return to terra and Ven thus many claim her character story arc ended but here is the thing, Aqua has PTSD after what happened to her in the realm of darkness and she needs to conquer it so her story was given more depth and minor continuation
9. Ventus story arc is still going even after he woke up because of his connection to Sora and Xehanort and Union X
10. Namine story arc to me has ended in kh3 when she was given a body to be her own person instead of just being a floating Ghost who is trapped in her room, she can be given a new role tho
that’s my conclusion on the characters, I believe not everyone should be removed just cause their story arc ended they can still keep some characters and develop them more