Well that's what I mean then there are hierarchies within the hierarchy. Ie: Paul is the least of apostles, John the Baptist is the least of the prophets, the laity is the least of the clergy, etc.
This is the context of this word about Paul being the least. He was given the dispensation of the grace of God. He has received the revelation of the mystery of Christ. He has been made a minister through the effectual working of God's power in Him.
8 Unto me, who am less than the least of all saints, is this grace given, that I should preach among the Gentiles the unsearchable riches of Christ;
Paul never said he was less than the least of all apostles. That is leaven that is critical to create a tradition of man. He said that He is "less than the least of all saints".
Now there are several ways to interpret that.
1. When he is weak then he is strong because he cannot do anything of himself. He understands that the true strength of His ministry is the word of God and the grace of God operating in the ministry. We see the same thing with Peter. He was the one who denied the Lord three times and yet he is also the one who takes the lead. It wasn't him, it was God operating in him as the least of all the saints at that time. This point applies to anyone who has a ministry, you can't rely on your own strength. Someone tells me they want to have a gospel music ministry because they have a great voice, I know that is doomed from the start. Someone tells me they want to help the church with the gospel because they are an accountant and were able to help a business become profitable, that is doomed from the start. These ones see their own strength as the key to their ministry. Paul saw that the grace of God was the key to his ministry.
2. We can say based on what he says elsewhere that he says he is least because of his involvement in the stoning of Stephen. His point is not simply that he was a sinner, but that his sin was in direct rebellion to the Lord Jesus and His move on earth. That is why the Lord's salvation of him included telling him what great things he must suffer. Stephen is gone because of him, he must take his place. This also applies to all of us. Because of our sins there are consequences. A guy who was a drug addict and gets saved will often have a ministry to drug addicts. He was led out of hell by the Lord, he now knows the trail to take to go and get others and lead them out. Each one of us found salvation, the path we took can become a ministry, similar to the underground railway to help lead others out of the slavery to sin.
However, you cannot interpret this to mean that he saw himself as below Peter or James in the hierarchy of apostles, all you have to do is read Galatians to realize that is not valid.