So now let us look at Hebrews 7:22. "By so much was Jesus made a surety of a better testament."
It is clear that the writer of Hebrews is addressing the changing of the priesthood from the physical Aaron to the Spiritual after the order of Melchisedec (Judah/Jewish) verse 15 of the same chapter. The better covenant is a "changing of the Administrator/Mediator" by an everlasting priesthood. That's why Moses was present at the "Mount of Transfiguration."
Lastly, let's look at Hebrews 8:6, but then in context along with verses 1 thru 5 plus verse 7 including 9:1, and let's see what the writer of Hebrews is actually addressing. I'll add verse 8:13 also.
"Now of the things which we have spoken this is the sum: We have such an high priest, who is set on the right hand of the throne of the Majesty in the heavens; A minister of the sanctuary, and of the true tabernacle, which the Lord pitched, and not man.For every high priest is ordained to offer gifts and sacrifices: wherefore it is of necessity that this man have somewhat also to offer.For if he were on earth, he should not be a priest, seeing that there are priests that offer gifts according to the law: Who serve unto the example and shadow of heavenly things, as Moses was admonished of God when he was about to make the tabernacle: for, See, saith he, that thou make all things according to the pattern shewed to thee in the mount.But now hath he obtained a more excellent ministry, by how much also he is the mediator of a better covenant, which was established upon better promises. For if that first covenant had been faultless, then should no place have been sought for the second. (13) In that he saith, A new covenant, he hath made the first old. Now that which decayeth and waxeth old is ready to vanish away. (9:1) Then verily the first covenant had also ordinances of divine service, and a worldly sanctuary.
The word covenant (highlighted in green) are not in the original text. Is this not the administration/Mediator of the priesthood from the old to the new? It isn't addressing what was to be administered, but who the New Administrator would be, and He is our Savior, and our High-Priest.
So what does our High-Priest say about all of His own Father's instructions since the beginning of time knowing God doesn't change and neither does Jesus? Malachi 3:6 Hebrews 13:8
"Then said Jesus unto them, When ye have lifted up the Son of man, then shall ye know that I am he, and that I do nothing of myself; but as my Father hath taught me, I speak these things." (John 8:28)
Did God's words change, or have some of God's words been deleted in Christ? I think not.
Was the "changing of the priesthood" in the plan from the beginning? I think so.