So you are saying that Brant said: "Mary IS sinless, but she could not be without the anticipatory merit of Christ on the cross. Even if, somehow, Mary never committed actual sins independent of the anticipatory graces of Calvary, she was still directly preserved from original sin by God because of what her role would be in Christ's mission on earth, which was to embrace the cross that we might attain eternal life."
then you lost me with "anticipatory merit"
Mary anticipated nothing. She was consecrated to God from age 3. The appearance of the Angel Gabriel took her quite by surprise, so much so that in her response she commented that she had never known a man. She was a virgin!
Bottom line: common sense tells us that God would be born of a pure vessel. There was no "backup" plan here. He prepared Mary for this role but asked her permission first. She accepted: "Let it be done unto me according to thine Word".
Imagine the reaction from those around her! What's not to love about this beautiful woman, our Mother!
Are you saying that she was NOT preserved from sin in anticipation of her Son's meritorious and salvific death on the cross? How ELSE was she preserved from original sin and given superabundant grace to avoid actual sin BEFORE Calvary? She certainly didn't do it solely on her own. She needed salvation, too, and benefitted from her Son's sacrifice just like we do. The only difference is that God applied the merits to her BEFORE the crucifixion, indeed, before the birth of Jesus. In other words, her preservation from sin was ANTICIPATORY to the cross. This was so she could be the spotless God-bearer fulfilling that which was presaged in the Ark of the Covenant. This is basic stuff. You need to check the catechism on this one. Either that, or you misunderstand what I am saying. I have no idea what you mean by your final three paragraphs, at least as they pertain to the discussion of anticipatory preservation from sin in Mary.