Consecrate the world to Mary? Not hardly. God alone is Sovereign. You do get that we don't see those activities as mutually exclusive.
We're an old church, with habits and diction perhaps best understood with reference to Troubadours, Medieval poetry and customs, and things of that kind. You might get SOME notion of the affect (if you know Tolkien) when you consider Gimli's fierce devotion to Galadriel. That's "courtly love" of a kind. A knight could be devoted to his lady, but that had nothing to do with marital love (Except in Parzival -- his "lady" is his wife! Astonishing!) The "lady" might be the queen or his lord's wife, and at least in the ideal, the lover's joy would be only to receive her smile and the privilege of bearing a token of hers - a veil or a bit of sleeve which she had once worn. There really was an ideal of a passionate love which either had nothing to do with sex or with VERY sublimated sex, and it was a love that dared and endured great things, either of courage or of asceticism.
And that lies behind the language, excessive to our ears, of some of the Western songs to Our Lady.
And MY Lady would never return my love if I betrayed my utter allegiance to my Lord and hers. The matrix within which my love arises is that my Lord loves her, and she and I love Him.
Again, it's a matter of flavor and of experience. My mother was English, as she said "A British subject, not an American object." She had quite ambivalent feelings about the aristocracy, of which she was by no means a member, but she LOVED the Queen. I was bowled over when I realized this about her, and it shed a new light on pre-Republican governments and why regicide was considered especially foul.
Then I was involved with a really neat candidate for our state assembly, a self-made man and a man of principle and faith. And I remember seeing him march in our little community's 4th of July parade (in which George Allen usually rides a horse, since he's from around here.) And as he passed I smiled and whistled and pointed at him, as if to say, "You da MAN!" and he saw me and smiled and pointed back, as if to say, "No, YOU da Man!" And it just felt good. Now if I were to write a song about that, somebody could say it sounded blasphemous or plausibly homosexual. But it would be no more blasphemous than the Four Tops song, "I'll be there," which I always thought with a little tweaking would make a great hymn.
Lewis says, in another comparison, that some art is like through difference, and the more like, the more unlike. A good painted portrait is more like the subject than all but the very best photographs. But photographs are in some sense "exact" representations.
So the Theotokos is, as are we all, in God's image. But my devotion to her is very unlike my devotion to God.
One last inadequate appeal. I am very devoted to my wife. I am also very devoted to my child. Those devotions do not conflict with one another or with my devotion to God. If anything, they all reinforce one another.
Again, I am not really trying to persuade. Maybe I'm suggesting that there is a range and subtlety to religious affect and affiliation which might be more nuanced than folks at first appreciate.
[Veneration of Mary] is not Scriptural In a similar sense as when you do word search for "consecration of bishop" and declare it not scriptural. Indeed, veneration of saints is not referred to in the scripture for the simple reason that this form of piety developed in the age of martyrs after the books of the Canon were written. The necessary elements of the veneration of all saints, and of course, especially Mary are in the multiple requests for intercession throughout the gospel (e.g. see the daughter of Jairus episode), and in the fact that the saints have eternal life in Christ ("To them indeed, who according to patience in good work, seek glory and honour and incorruption, eternal life", Romans 2). To read more, see Communion of Saints.
As Catholics we do not think that our devotions and pieties need to be explicitly mentioned in the scripture. We also do not put too great a stock in pronouncements of unscripturality coming form the Protestants, since in their case the fundamentals of their theologies are not merely unscriptural but counterscriptural.
Veneration and devotions to the Blessed Mother come in addition from her essence as the Mother of God who adopted us all at the foot of the Cross. "All generations shall call me blessed", she predicted. We understand that she participated int he mystery of the Incarnation in a unique way. There is no reason to think that she would not wish to bring the divine plan of salvation to its most glorious fruition also now; and if so, certainly she will add her prayers to ours as we plead for Christ's mercy.
Specifically you refer to the mediatorship of Christ. You forget, however, that in the same passage where His role as the sole mediator is described, intercessory prayers are also prescribed:
1 I desire therefore, first of all, that supplications, prayers, intercessions, and thanksgivings be made for all men: 2 For kings, and for all that are in high station: that we may lead a quiet and a peaceable life in all piety and chastity. 3 For this is good and acceptable in the sight of God our Saviour, 4 Who will have all men to be saved, and to come to the knowledge of the truth. 5 For there is one God, and one mediator of God and men, the man Christ Jesus: 6 Who gave himself a redemption for all, a testimony in due times. (1 Timothy 2)
It should be clear that a prayer to Mary or to a saint is a prayer to Christ; but it is a stronger prayer as now two of us pray, me and her.
pray one for another, that you may be saved. For the continual prayer of a just man availeth much (James 5:16)
Your other specific objection is to consecrating the world to Mary, because "God alone is sovereign". Biblically, it is not a contradiction: as Christ is King, Mary is Queen Mother. Her last recorded word is "do as He tells you". We listen.
The Coronation of the Virgin
Gentile da Fabriano
The J. Paul Getty Museum