For years, theologians and clergy have considered and promoted the appropriate nature of declaring a fifth Marian dogma.  The so-called title, "Mary, Coredemptrix, Mediatrix, and Advocate", has been bandied about since the Church-approved apparitions of "Our Lady of the Nations" which took place in Amsterdam, Holland, from 1945- 1959.  The Blessed Mother, it is said, told the visionary Ida Peerdman that she wished for this dogma to be proclaimed as the "final and greatest" Marian dogma. 
Support for this dogma has grown through the decades since, however, due to general misunderstanding of the terms, "Coredemptrix" and "Mediatrix", the effort has been stalled.  In short, the term "Coredemptrix" does not imply Mary having equal footing with Jesus, but only that she "assisted" and "participated" with  Jesus in the redemption of mankind, first, by consenting to His incarnation in her womb, second, by her witness at the Cross and reception of all the faithful as her children.   The term "Mediatrix" does not remove Christ from the role of the sole mediator between God and man.  Instead, she is the great mediatrix between her children and Jesus, her Son, and all grace, therefore, flows from the hand of her Son, through her, and out to the world.  

Time will tell when this dogma will be proclaimed, but what the Blessed Mother asks for from Her Son, she receives.  Maybe not today, maybe not this century, but certainly.  

The following are Church documents proclaiming Marian dogma:

     

     

The following are Church documents supporting Marian doctrines of the Church held in Tradition:

     

       

In short, the Successor of Peter (and the bishops in union with him) has the power to "bind and loose" both in heaven and on earth.  Even the Blessed Mother is bound to the decisions of Peter -- in this case, with regard to the graces she can bestow upon the faithful.  We don't believe that Peter can "bind" the Blessed Mother, but the operation of extraordinary grace under a specific title is dependent on the solemn definition of that title.  In other words, some dude in his garage can't set up a shrine to "Our Lady of Craft Beer" and expect to receive graces.   And although we receive grace from Mary when we call upon her as "Mary, Queen of Heaven," it does not match the flood of grace that was released to the world when, for example, the Assumption of Mary was solemnly defined.  
     
Practically speaking, a "dogma" is the "final word" on an Eternal Truth.  Whereas we continue to ruminate on "Mary, Queen of Heaven", or "Mary, Mother of the Church", Peter has declared that the Church's teaching of Mary's Immaculate Conception is entire and requires no further development doctrinally.  As Christ promised, Heaven ratifies these solemn definitions by the previously mentioned flood of grace under the dogmatic title.  So when people clamor for a new Marian dogma to be declared, it's for two reasons:

1)  It puts any debate to rest.  Forever. 

2)  It draws down a flood of grace to the world (like an open spigot) when Our Lady is called upon through those titles.