Personally, I hope this dogma is not authoritatively defined because it doesn’t need to be. Things should only be defined when there is confusion and if it is edifying to the faithful.
We all know that the Blessed Mother helped Christ in his redemptive work by agreeing at the Annuciation, and by commanding his disciples to “do whatever he tells you” during the wedding at Cana. We also know that Our Lady has helped convert many sinners to Christ.
However, the dogma of “Co-Redemptrix” will only add to the confustion about Mary amongst Protestants and many faithful. Nothing will change if this dogma is defined; although I do think it will cause many people stress, particularly those within the Eastern rites who have had to deal with many latinizations over the years.
The reasoning behind this title is sound theologically, but I don’t see the need to declare this theological opinion as necessary for belief.
Furthermore, I do not see how this can be seen as an Apostolic belief. I know that the Eastern Orthodox would most certainly disagree with this dogma.