I was invited to speak to the ELCA Conference of Bishops on this topic at their annual academy a couple of weeks ago (to which they invite the ELCIC Bishops as well) along with Dr. Guy Erwin who teaches Reformation history at California Lutheran University. I gave two presentations: "The Evolving Office of Bishop in the ELCA" which gave some historical perspective on how oversight was exercised in predecessor church bodies in the U.S., and "The Role of the Bishop in the Lutheran Church Today in Light of the Marks of the Church." I treated the marks of the church in reverse order following the lead of missiologists such as Darrell Guder.
In my research for these presentations, I came across an LWF Document that was adopted in 2007: Episcopal Ministry Within the Apostolicity of the Church. This document is a revision of a 2002 draft that was widely distributed. Responses were invited from various theologians and groups including the WordAlone theological advisory board. In my view, the 2007 Lund Document is a very helpful and clarifying treatment of what has become a contentious issue in the ELCA. My only critique is that the section on Mission (III) should have preceded and thus framed the Biblical and Historical Foundations in II.