In 1 Peter 5:1-4, Barth’s statement that the “unity and universality of the Church’s ministry will always be, not a beautiful ideal, but the absolute law of the community, and therefore that which must be maintained as the conditio sine qua non of its life” (695) is best supported by 1 Peter 5:3, where elders are commissioned to be examples to the flock. In light of 1 Peter 4:7-11, the implication is that the individual members of the flock are to serve one another, and that the elders are to be exemplars of this service, but also of the attitudes described in 5:2-3 and 4:7-9.
Barth nuances his argument by saying that “the service of the community is a differentiated service” (694) and his description of the church is inspiring (in contrast, for instance, to clergy-focused visions of the church like that painted by Pope Pius X in Pascendi Dominici Gregis (Feeding the Flock of the Lord) (1907)), but just what does he mean by “the Church’s ministry”? Providing services associated with what Luther described as “the kingdom of the right hand” like preaching (public evangelism) and administering the sacraments? If so, I fail to see why the responsibility for providing these services should be foisted upon every church member instead of delegated to those in whom the church has recognized gifts for this ministry and called to provide service of this kind. But I doubt that Barth means only word and sacrament service. If he imagines something more expansive, what boundaries does he have in mind? If he simply means that every church member should be involved in offering goods and services to others, is he proposing that church elders attempt to oversee the markets in which these goods and services are exchanged? Or should Christians withdraw from “secular” markets and participate only in a Christian command economy overseen by church elders, as in Hutterite colonies?
Furthermore, Barth’s apparent infatuation with the universal rather than the particular (see, e.g. the final sentence of the main paragraph on p. 694) makes me skeptical of the efficacy and benefit of his words in pastoral work. In contrast, the eautous / allelous language of 1 Peter 4:8-10 keeps the focus of service appropriately on the local and particular, evoking fruitful and incarnate images of service that can be offered by/to real people in real places at real times. According to 1 Peter’s model, then, the church is built together as a natural consequence of a local, deontological ethic, rather than as the result of a centrally administered Five Year Plan, and becomes a spiritual house in which God dwells and from which the gospel of Jesus Christ is proclaimed in word and act.
Thanks for letting me look over this. Your concerns are well stated and thoughtful, although - in my humble opinion - they do not finally stick. But, I can only say that because of other things I have read in Barth that clarify what he is saying in the section of CD 4.2 with which you are working.
The fundamental point of Barth's ecclesiology is that the church is sent as God's witnesses into the world. This is what he means what he talks about ministry and service. This includes, of course, the maintenance of the sacramental and communal life within particular churches, but it is also much more than that as the church moves outside of itself. This factors into ordination. All Christians bear this same vocation of witness, and so Barth does not want to divide the church up into a serving / ministering clergy and a receptive laity. The status of clergy, then, is reduced to a particular function within the community and as part of the community's witness to the world. This is a radical Protestant rejection of the Roman sacrament of ordination. It is also what gives rise to the more "universal" feel of Barth's ecclesiology in contrast to his usual penchant for the "particular" - he handles ecclesiology more universally because he thinks that each particular church has the freedom to structure itself in a way befitting to its mission of witness in its particular context. However, this does not mean that his ecclesiology is “abstract,” for it proceeds with constant reference to Jesus Christ.
If you want to study Barth further on these things, the place to turn is Church Dogmatics 4.3.2.
Grace and Peace,