I *do* wish you wouldn't make stuff up and call it "Catholic reasoning". You'd do better to put that in the form of a question, e.g. "Wouldn't it follow from Catholic doctrine that...?"
Why say God had just two choices? There's a third.
Open your Bible and see how the predestination and consecration of Mary are repeatedly foreshadowed in an unbroken chain of types, figures, and prophecies concerning the Incarnation, which necessarily involves Mary, the Mother of the Incarnation.
Right from the beginning (Genesis) God says to Satan , "I will put enmities between thee and the woman, and thy seed and her seed; "that" (ipse) shall crush thy head, and thou shalt bruise his heel" (Gen. 3: 15). So right from the beginning, war is declared between the Seed of the Serpent and the Seed of the Woman: a seed is being prepared which will defeat the ancient Adversary.
What was God doing in the OT? Here's a succinct and summary answer: preparing the seed.
In this Genesis protoevangelium, the Redeemer Himself is mentioned only in relation to "the woman"; He is "the woman's" seed; a very peculiar expression, showing one born in some wonderful manner, not according to the ordinary laws of generation. It points unmistakably to the Blessed Mother and her Child. Thus the two adversaries, whose combats make up the history of the world, are, on one side, the devil, on the other, the woman; and again, the seed of the devil and the seed of the woman.
I could go through the rest of the Bible book by book identifying the prophecies and types (and there is more about Mary in the OT than in the NT) but for now, let me just conclude that Mary's existence was being planned out by God from the dawn of the human race. She was neither an ordinary single gal nor an ordinary married woman, but "chosen in Christ before the foundation of the world," a Woman Predestined.
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Nevertheless, she would either be married or single.
We are ALL chosen in Christ. Read Ephesians 1 where the word for grace there is the same one used by the angel to Mary.
Mary and Grace
The word grace used in this passage in Luke is used in one other place in the Bible and that is Ephesians 1 where Paul tells us that with this same grace, God has blessed us (believers) in the Beloved. IOW, we all have access to that grace and it has been bestowed on us all.
http://biblehub.com/greek/5487.htm
Luke 1:28 And he came to her and said, Greetings, O favored one, the Lord is with you!
Ephesians 1:4-6 In love he predestined us for adoption as sons through Jesus Christ, according to the purpose of his will, to the praise of his glorious grace, with which he has blessed us in the Beloved.
Greek word grace
charitoó: to make graceful, endow with grace
Original Word: χαριτόω
Part of Speech: Verb
Transliteration: charitoó
Phonetic Spelling: (khar-ee-to'-o)
Short Definition: I favor, bestow freely on
Definition: I favor, bestow freely on.
HELPS Word-studies
Cognate: 5487 xaritóō (from 5486 /xárisma, "grace," see there) properly, highly-favored because receptive to God's grace. 5487 (xaritóō) is used twice in the NT (Lk 1:28 and Eph 1:6), both times of God extending Himself to freely bestow grace (favor).
Word Origin: from charis
Definition: to make graceful, endow with grace
NASB Translation: favored (1), freely bestowed (1).