SwapCharacter.cs

using UnityEngine;
using UnityEngine.AddressableAssets;

public class SwapCharacter : MonoBehaviour
{
    [SerializeField] Animator parentAnimator; // 登録するAnimator

    private GameObject cacheCharacter; // 差し替え時に元オブジェクトを削除する用

    public void Load(string characterName)
    {
        Addressables.Instantiate(characterName, parentAnimator.transform, false).Completed +=(res)=>
        {
            // 以前のキャラ情報を破棄
            if( cacheCharacter != null)
                Addressables.ReleaseInstance(cacheCharacter);
            cacheCharacter = res.Result;

            // 再構築
            var childAnimator = res.Result.GetComponent<Animator>();
            parentAnimator.avatar = childAnimator.avatar;
            parentAnimator.Rebind();
        };
    }
}