This matter of what to call the Most Holy Theotokos, who is a heretic and who isn't, was settled by The Church over 1600 years ago. It seems to me that since most of the proceedings of the Ecumenical Council at Ephesus are online, perhaps everyone should read them. Here's a link:
http://www.ccel.org/ccel/schaff/npnf214.x.ii.html
Just keep clicking "next" and you'll find all you need to know and then some. Accepting it or rejecting it is of course up to you individually.
Now as for heresy and heretics, well, The Church has pronounced its anathema through +Cyril at that Council thusly:
"If anyone will not confess that the Emmanuel is very God, and that therefore the Holy Virgin is the Mother of God (Θεοτόκος), inasmuch as in the flesh she bore the Word of God made flesh [as it is written, “The Word was made flesh”] let him be anathema."
Now you can split all the hairs you want. The Church has seen them split before and likely more than you can think of. Unless you can accept the foregoing formulation without qualification, The Church declares you a heretic, cut off from The Church and as such there is nothing She can do for you until you repent. You are classed with Arius, Nestorius and a whole host of others. Likely the anathema of The Church will not bother you. You don't accept The Church (or the pronouncements of the 7 Ecumenical Councils) as we Orthodox and Catholics (and some Lutherans) define it. The Pope of the "Elder See at Rome" has declared that your communities are not properly churches but rather are "ecclesial communities" in great measure because of this. You don't accept that either and I am sure it causes you no lack of sleep. But there it is. Arguing with Catholics or Orthodox and/or some Lutherans about this is a total waste of time and bandwidth on both sides. The simple fact of the matter is that most Protestant Christology and Trinitarian theology has been and is branded heresy by The Church. That isn't going to change and I doubt any of you will.
To my Lutheran, Catholic and Orthodox brethren, these threads offer us an opportunity to become educated on what Protestants and others believe (for which I am very grateful) and vice versa, but after awhile, when heresy as defined by the Councils rears its head, it becomes a mistake to continue. Remember these words of +John Chrysostomos in his 6th Homily on Titus:
"By Contentions," he means, with heretics, in which he would not have us labor to no purpose, where nothing is to be gained, for they end in nothing. For when a man is perverted and predetermined not to change his mind, whatever may happen, why shouldest thou labor in vain, sowing upon a rock, when thou shouldest spend thy honorable toil upon thy own people, in discoursing with them upon almsgiving and every other virtue?
How then does he elsewhere say, "If God peradventure will give them repentance" (2 Tim. ii.25); but here, "A man that is an heretic after the first and second admonition reject, knowing that he that is such is subverted and sinneth, being condemned of himself"? In the former passage he speaks of the correction of those of whom he had hope, and who had simply made opposition. But when he is known and manifest to all, why dost thou contend in vain? why dost thou beat the air? What means, "being condemned of himself"? Because he cannot say that no one has told him, no one admonished him; since therefore after admonition he continues the same, he is self-condemned."
The Church can not call cursed what Christ has blessed. Sorry. My hope is in Christ Jesus Himself, not the church.
Well for starters, I won't call her "Most Holy" as the scriptures say there is none good but God and all our righteousness is as filthy rags. So there is only one "Most Holy" and it wasn't Mary.
(Isaiah 6:3 KJV) And one cried unto another, and said, Holy, holy, holy, is the LORD of hosts: the whole earth is full of his glory.
(Revelation 4:8 KJV) And the four beasts had each of them six wings about him; and they were full of eyes within: and they rest not day and night, saying, Holy, holy, holy, Lord God Almighty, which was, and is, and is to come.
(Daniel 9:24 KJV) Seventy weeks are determined upon thy people and upon thy holy city, to finish the transgression, and to make an end of sins, and to make reconciliation for iniquity, and to bring in everlasting righteousness, and to seal up the vision and prophecy, and to anoint the most Holy.
I am behind on the thread, but I intend to continue. This is why: when Christ said "why persecutest thou me?", the actual persecution was against the Church.
Christ is Church.
There are no new heresies. All this reform stuff is a rehash of what greater heretics had thought. As long as the Church exists, she will have enemies. The Apocalypse tells us that Our Lady is forever the target. Without sounding pretentious, it is, really, a cosmic battle. Why is it a mistake? Why stay away? Don't go anywhere.