OK, 'Devils Advocate', if there was nothing super-special about Mary, why was she chosen for the role ?
Protestants seem to agree that she was a 'sinner'. Surely there were heaps of similar women around at the time.
With an acceptable lineage - (which seems to have importance for some).
I am not protestant but to answer your question there does not have to be anything more special about a person then another for God to choose them..............
The bible all throughout it shows God choose people who were guilty of murder and prostitution to do His will.
Just because Mary was chosen to be the carrier of God in the flesh, our Lord Jesus Christ does not mean she was any more special or sinless then any other person. The bible makes it clear only one person who walked this earth was sinless, and that was the Lord Himself.
Moses was raised and Egyptian that persecuted others and even murdered another man, yet he was chosen by God for a major purpose in God's plan.........
Rahab was a prostitute that was chosen by God to do His will and protect the Israelites that came to her..........
Apostle Paul who was charged to be the main Apostle to the Gentiles was a murder and persecutor of other Christians before chosen by God to do this..............
So nowhere does the bible say a person has to be special as in sinless, or be walking properly to be used........