I don’t know what St. Francis said about it, but I think it’s an interesting question.
Note that our profession doesn’t simply say “for our salvation”, it says “for us men and for our salvation.” So one might ask, if salvation wasn’t required, would He still have been incarnated for us? Remember that the primary image we have for the Son’s relationship with us is that of Bridegroom and Bride. Would that have been negated if the Bride didn’t need to be redeemed? Would He have chosen not to wed Himself to us?
We know that His primary purpose in Incarnation was our Salvation. That was the Father’s purpose for sending Him. But that’s to a fallen humanity. This doesn’t mean He would not have sent Him for another purpose if Salvation wasn’t needed.
Our ultimate purpose is theotokos. We are meant to be united to God, to enter into His Divine Family, to share in His Life. This was always our purpose, even before sin. So the I think in order to answer this question, we should consider whether Incarnation was ever necessary for that end.
I don’t think St Francis said anything about it. If I’m not mistaken, the idea that the Son of God would have become incarnate even if Adam and Eve had not sinned is the work of Blessed Duns Scotus who was a franciscan philosopher and theologian in the 13th century. I’m not sure what St Bonaventura’s opinion is on the matter; he was also a franciscan.
Thomas Aquinas addresses the question as well in the Summa Theologica, Part III, q. 1, art. 3. He says:
Augustine says (De Verb. Apost. viii, 2), expounding what is set down in Luke 19:10, “For the Son of Man is come to seek and to save that which was lost”; “Therefore, if man had not sinned, the Son of Man would not have come.” And on 1 Timothy 1:15, “Christ Jesus came into this world to save sinners,” a gloss says, “There was no cause of Christ’s coming into the world, except to save sinners. Take away diseases, take away wounds, and there is no need of medicine.”
I answer that, There are different opinions about this question. For some say that even if man had not sinned, the Son of Man would have become incarnate. Others assert the contrary, and seemingly our assent ought rather to be given to this opinion.
For such things as spring from God’s will, and beyond the creature’s due, can be made known to us only through being revealed in the Sacred Scripture, in which the Divine Will is made known to us. Hence, since everywhere in the Sacred Scripture the sin of the first man is assigned as the reason of Incarnation, it is more in accordance with this to say that the work of Incarnation was ordained by God as a remedy for sin; so that, had sin not existed, Incarnation would not have been. And yet the power of God is not limited to this; even had sin not existed, God could have become incarnate."
In the CCC “Why did the Word become Flesh” it says:
With the Nicene Creed, we answer by confessing: “For us men and for our salvation he came down from heaven; by the power of the Holy Spirit, he became incarnate of the Virgin Mary, and was made man.” (#456)
In expounding on this article of the creed, the first thing the CCC says is:
The Word became flesh for us in order to save us by reconciling us with God, who “loved us and sent his Son to be the expiation for our sins”: “the Father has sent his Son as the Saviour of the world”, and “he was revealed to take away sins” (#457).
The quotes here are from 1 John 4:10, 4:14, 3:5. The CCC next lists some other reasons for the incarnation which are very fitting.
The first announcement of the Messiah or the Redeemer is in the protoevangelium (the first gospel); Genesis 3:9, 15; CCC#410. This announcement came after the sin and fall of Adam and Eve, not before it.
I agree with Aquinas then that everything in Holy Scripture which is really all we can go by on the question at hand, without speculating or guessing as it were, points to the incarnation as a remedy for sin even though as Aquinas says, even without sin, God could have become incarnate.
As far as the Bridegroom and Bride relationship, Adam and Eve were already the brides of the Son of God through sanctifying grace and original holiness and justice they were created in before their fall. Sanctifying grace puts us in this relationship with God and Adam and Eve possessed sanctifying grace before they sinned and before the Son of God became incarnate.
Theologians, following St Augustine, generally hold that the incarnation was not absolutely necessary even as a remedy for sin, but that it was most fitting. God who is omnipotent could have saved the human race by some other means.
