IEnumratorをある程度同時実行しつつ、全部完了するまで待機してくれる感じの奴

ParallelCoroutineQueue.cs

using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;

/// <summary>
/// 指定した数だけ同時実行するコルーチンのキュークラス;
/// 実行されるコルーチンはtargetBehaviourを使って生成され;
/// exeCoroutineにパスワードと共に登録する;
/// コルーチンは役目を終えたら;
/// 自らexeCoroutineに登録してるパスワードから自身を停止状態であると教える;
/// </summary>
public class ParallelCoroutineQueue
{
    public class KeyCoroutine
    {
        /// <summary>
        /// 登録コルーチン;
        /// </summary>
        public Coroutine ExeCoroutine { get; set; }

        /// <summary>
        /// パスワード;
        /// </summary>
        public string Key { get; set; }

        /// <summary>
        /// 実行中;
        /// </summary>
        public bool IsRunning { get; set; }
    }

    #region DECLARATION

    /// <summary>
    /// 同時実行の制限値;
    /// </summary>
    public int ParallelLength { get; set; } = 5;

    private Queue<IEnumerator> entryEnumerators = new Queue<IEnumerator>();

    private List<KeyCoroutine> exeCoroutine = new List<KeyCoroutine>();

    private MonoBehaviour targetBehaviour = null;

    #endregion // DECLARATION;

    #region FUNCTION

    /// <summary>
    /// IEnumeratorの追加;
    /// </summary>
    /// <param name="enumerator"></param>
    public void Add(IEnumerator enumerator)
    {
        entryEnumerators.Enqueue(enumerator);
    }

    /// <summary>
    /// 追加したIEnumerator達を実行していく;
    /// 全部実行したら終了になる;
    /// </summary>
    /// <param name="mb"></param>
    /// <returns></returns>
    public IEnumerator WaitForCoroutine(MonoBehaviour mb)
    {
        targetBehaviour = mb;

        do
        {

            for (int i = 0; i < exeCoroutine.Count; ++i)
            {
                yield return exeCoroutine[i];
            }

            exeCoroutine.RemoveAll(item => !item.IsRunning);

            while (entryEnumerators.Count != 0 && exeCoroutine.Count < ParallelLength)
            {
                AddExeCoroutine();
            }

        } while (entryEnumerators.Count != 0 || exeCoroutine.Count != 0);
    }

    private IEnumerator ExeCoroutine(IEnumerator enumerator, string path)
    {
        yield return enumerator;
        ComplateExeCheckPath(path);
    }

    private void AddExeCoroutine()
    {
        // 10桁のパスワードを作る;
        var key = Guid.NewGuid().ToString("N").Substring(0, 10);

        var coroutine = targetBehaviour.StartCoroutine(ExeCoroutine(entryEnumerators.Dequeue(), key));

        exeCoroutine.Add(new KeyCoroutine()
        {
            ExeCoroutine = coroutine,
            Key = key,
            IsRunning = true,
        });

    }

    private void ComplateExeCheckPath(string key)
    {
        for(int i = 0; i < exeCoroutine.Count; ++i)
        {
            if(exeCoroutine[i].Key == key)
            {
                exeCoroutine[i].IsRunning = false;
                return;
            }
        }
    }

    #endregion // FUNCTION;

}