God sure would have been stymied, wouldn't He?
Imagine the bind He'd have been in if Mary had said no. That would have ruined everything.
I guess God's not smart enough to have contingency plans, eh?
“God’s not smart enough to have contigency plans, ...”
It’s not about contingencies. It’s about free will. Eve chose to say yes to Satan thereby closing the gates of heaven.
The only way to cancel out Eve’s mistake and simultaneously preserve mankind’s free will was for Mary to choose with her free will to say yes to God.
Mary’s yes is the perfect parallel to Eve’s no. Any contingency would wipe out our free will. God preserves our free will at all costs, even if we freely choose hell.
That’s why we love the Blessed Mother. If she had said no the gates of heaven would remain closed.