“through the intercession of the Virgin Mary, His Mother”
Yes, this would be a practical result of Mary being understood as “co-mediatrix.” And, yes, I know that the intercession of other saints is also invoked, who are not considered co-mediators. Which brings us to another point. Where are we commanded or encouraged to seek the intercession of those already in heaven? And, no, I am not denying that those in heaven pray/speak to God, and surely not to our detriment. But where does it say that they hear our prayers? Or that we should pray to them? There are many questions and problems here that have no Scriptural basis.
“co-mediatrix” shines the light on Jesus as the one mediator between God and man. it is not about Mary, same as Mother of God.
the problem you have with the communion of saints is sola scriptura and a misunderstanding of the Body of Christ. the saints are in Christ and are very much aware of what is happening on earth. Read Revelation, the martyrs cry out “how long until they are avenged” the angels are aware of what is happening on earth, are the saints in heaven less than the angels? again, sola scriptura robs one of the complete Faith.