One certainly can't put Ambrose in your camp:
The first thing that kindles ardor in learning is the greatness of the teacher. What is greater (to teach by example) than the Mother of God? What more glorious than she whom Glory itself chose? What more chaste than she who bore a body without contact with another body? For why should I speak of her other virtues? She was a virgin not only in body but also in mind, who stained the sincerity of its disposition by no guile, who was humble in heart, grave in speech, prudent in mind, sparing of words, studious in reading, resting her hope not on uncertain riches but on the prayer of the poor, intent on work, modest in discourse; wont to seek not man but God as the judge of her thoughts, to injure no one, to have goodwill toward all, to rise up before her elders, not to envy her equals, to avoid boastfulness, to follow reason, to love virtue. When did she pain her parents even by a look? When did she disagree with her neighbors? When did she despise the lowly? When did she avoid the needy? (ibid., 2:2:7).
He may not of thought she was concieved without sin but he certainly indicated she lived a life without sin.
