Thank you for sharing your insights and for all your pings!
It seems pretty straight forward to me that Jesus' ministry was not about replacing the legalistic structure of the Pharisees and Sadducees with another structure of the same ilk. I believe God telling Israel that he did not want Kings is a foreshadowing of this as well.
God wants us to trust in him. The Holy Spirit guided the creation of the Canon so that we would always have a sure foundation to find the truth and not be misguided by the social, or political pressures, of the day.
I think it's interesting that the merger between State and Religion occurred after the Canon was recognized. It could well be that the Holy Spirit was ensuring that when the pressures of the State began to try and change how we would understand God there would always be SCRIPTURE to testify to the truth.
It's interesting that in the other passages that correspond to Matthew 16:18 (Mark 8:27-30, Luke 9:18-20) that there is no indication of special status for Peter, or for the Apostles. I believe the keys to the Kingdom of heaven is the Holy Spirit and those that are bound are those that believe in Jesus, just as Peter had just done, and those that don't are loosed in heaven.