The following quotes are from William O. Gregg, "By Solemn Prayer and the Laying-on of Episcopal Hands". Ordination and implementing Full Communion," by, in Sewanee Theological Review, 40:2, 1997. The article urged both Episcopalians and Lutherans to reassess their positions in order to adopt the Concordat. (Italics are added.)

This office [of bishop] possesses inherently sacramental content and dynamics. That is, it is a means or instrument though which grace is effectively conveyed from God to the People of God. God's activity in and through bishops is not dependent upon the character of the person. The sacramentality of the office means that it possesses a natural capacity to be an instrument of God's self-gift to the church and to the world; the person who is bishop becomes a living, real, and permanent part of this sacramental symbol. Further, the sacramental symbol is inherently relational and expressive of the mutual participation of God and God's people in each other. Therefore, the person in office does become someone in a particular, permanent relationship with God and the church, and this relationship has distinctive authority and responsibility within the church for God people. Through the office, which becomes embodied in and though the person who is bishop, God and God's people meet as the bishop exercises sacerdotal and pastoral care of the flock and as the bishop and people gather to offer to God the symbols of their life and labor, hear and respond in faith to God's Word, and celebrate the sacraments. Moreover, in the bishop are brought together the local and universal realities of the church. In each congregation the bishop symbolically makes present the whole church catholic, and the congregation becomes present to the church catholic. (p.218)

...and therefore -- at least in the current liturgical text [i.e. the Ordinal]-- there is in some sense an ontological dimension to becoming and being a bishop. (p. 219)

Episcopalians need to understand that the way Lutherans speak of the ordained ministry entrusted to the church is a single ministry of Word and Sacrament within which there are persons who are called to fulfill certain specific aspects of that whole ministry. Episcopalians also need to understand that the way we speak of this reality is a single sacramental and pastoral ministry of Word and Sacrament which is extended through the bishop to the offices of priest and deacon. (p. 225)

For a time both churches will exist in a transitional phase toward full communion while we become knit together on a new and deeper level as Episcopalians and Lutherans through the historic episcopate. During this transition it is reasonable and appropriate - based on the commitment to the goal of bishop, priest, and deacon as the form of the ordained public ministry of Word and Sacrament -- for ECUSA to suspend the requirement of episcopal ordination in recognition of current Lutheran ordinations. Such a temporary suspension is also consistent with our having already mutually recognized each other as authentic churches... (p.227)