Well, the lack of "Biblical testimony" did not keep most of the Protestant reformers from accepting the tradition of the Church with regard to this matter, nor the doctrine of the Trinity as laid down by the ecumenical councils. Of course, many Protestants are actually Nestorians but do not acknowledge the fact. Marianology is so closely linked to Christology, that where one "demotes" Mary, one tends to demote Christ. Neglect of Mary can take bizarrre. I attended a Methodist wedding at Xmas time in Maryland. There was a manger scene in the Church, but no statue of Mary. I asked why not, and got a strange reply. "We just don't do that." Did Jesus just pop out of the air?
*****"...with regard to this matter, nor the doctrine of the Trinity as laid down by the ecumenical councils."
Do you know of anything regarding the doctrine of the Trinity as put forth by the councils that can not be referenced by Scripture?
*****"many Protestants are actually Nestorians"
I don't know of any that woud hold to Nestorian heresy - except the liberal, and they are only half-Nestorican (Jesus only had a human nature).
*****"Marianology is so closely linked to Christology, that where one "demotes" Mary, one tends to demote Christ."
My concern is that the exalation of Mary is an attack on the unique ness of Christ. I hear Catholic teaching and theology that ascribes to Mary attributes which in the Bible I only find ascribed to God. I don't mena to provoke here - just being honest.