"Mary has any other role in redemption other than that of Jesus' mother"
That's a pretty big role!!!
I, as a Christian, believe in eternal life and believe that Mary, just as any true believer, is in Heaven worshiping her Son. I also belive, as did those at the wedding feast at Cana, that she can intercede for me as well as, if not better, any human on earth can.
God is all powerful and all merciful. He can bring any one to Him in anyway He chooses. The world first knew its Savior through His mother. It does not surprise me that once again, God chooses to bring people to Him through His mother again. Just as God works through those living on earth, so too does He work with those living in Heaven.
However He chooses to extend His grace and mercy, I thank and praise Him.
Bless you!