I know, +Peter was in a "trance." Sometimes, biblical stories amaze me.
The problem I see with this (rather convenient vision) is why did God bother giving Moses the Law? In the Hebrews, it is clear that it was not the Covenant with God that was at fault but that the people of Israel made it faulty. The New Covenant prophesied in the Old Testament is for for the Jews, as the Old One was, and not for the Gentiles.
In the purity laws in particular, I see Mary, and in the OT law in general, and expression of God's desire to be with us and teach us how to be with Him. The Tabernacle had to be ready for Christ to come.