As a Non-Catholic Christian, I don't see why, other than mentioning that she is Jesus' mother, Mary has to play into a sound understanding of Christology. You know the councils well. People went back and forth between is He all God and no man? Is He part God and part man? Is He all man carrying the Attributes of God? Etc., etc.,
At that time, using the term Theotokos MAY have helped clarify somthing - though I still believe Mother of Jesus suffices. Today, with Mary as Co-Redemptrix, Mediatrix, Advocate, Savior, and Creator of the Sabbath (as many Catholics believe), calling her Mother of God is just one more loaded term we could do without. Look at the discussion! We have folks denying that she ever felt pain when Jesus was born. She felt pain during His lifetime. A sword pierced through her heart too as His mother. But, we can't even let her be a normal human being and have to ascribe things to her that the Bible never does.
Such is a horrible injustice to God. To think that the God of the Universe, who sanctifies us, couldn't use a vessel like us (with original and other sin), sanctify it and bless her as the bearer of His Son? No. We have to have Mary not only being sinless but being immaculately conceived as well. It isn't right and it takes glory away from God by creating an alternate object of devotion. We are never told to be devoted to anyone other than God Himself. The Holy Spirit, when he came wouldn't even testify of His person but of Christ alone. And we are supposed to sanctify things to Mary's honor and glory?
She was a woman. A beautiful and holy woman. But just a woman. She wasn't higher than the rest of us. She wasn't sinless. She was blessed and faithful and we should admire her but not to the point that she becomes the object of our devotion.
As an Orthodox Christian, I do not change doctrines or terminology to fit fashion. The mind of the Church understands 'Theotokos' to clarify and guard the same truths now as in 431, 'Christotokos' still denys them. Nor does the Church insist that the canon of Scripture, our primary written testimony to Christ, to God, and to the history of our salvation is exhaustive.
Some of your complaints about Latin mariology are just, though you probably frame them for the wrong reasons. We Orthodox regard the 'Immaculate Conception' as a jury-rigged fix to paper over a disconnect between the Latin (mis)understanding of Ancestral Sin (termed 'Original Sin' in the West) and the Church's long teaching concerning Mary's purity. While we're at it, though Mary was, indeed, assumed bodily into heaven, it was after her death (a point the Latin declaration of the dogma of the Assumption deliberately leaves ambiguous, as a large faction among the Latins hold that she did not die. As I understand it, it was concern for a hoped for reunion with the Orthodox that restrained the Pope, who himself held the view that Mary did not die, from including language to that effect in the proclaimation.)
There is an Orthodox objection particularly to the conjunction of the Immaculate Conception and a deathless bodily assumption, as it makes Mary nature not ours, but a pre-lapsarian Adamic nature. 'Not assumed, not redeemed' was the cry of the Fathers against monothelitism and monergianism, on which basis, I would argue that Mary's nature being other than ours vitiates the basis of our salvation as effectively as separating Christ's person or denying either of His natures.
Nonetheless, the tradition of the Church is that Mary (and the Prophet, Forerunner and Baptist John), while not sinless in the sense that Christ is sinless, nonetheless did not commit personal sin. (I have a dispute with my priest, who takes the more extreme view that this includes involuntary sins as well as voluntary sins, while I incline to the view that it includes only voluntary sins.) It has also, always been the understanding of the Church, East and West, that she was preserved from the pangs of childbirth (which the Fathers associate with the passions and the engendering of children through sexual intercourse, so if you'd like a Scriptural text to support the Church's position, look in Genesis), but experienced their anguish and more when the 'sword pierced through her heart' seeing Him on the Cross.