In his book, Priest and Bishop Fr. Raymond Brown makes the argument that, theoretically it should (or could) be possible for different forms of church polity to coexist in one communion. He argues:
The likelihood that in Paul’s lifetime some of his Churches that had no bishops lived in fellowship with Churches that had bishops suggests the possibility of two such Churches living in union today. The probability that not all the presbyter-bishops of the years 80-110 could trace their position back to appointment or ordination by an apostle suggests the possibility of our openness to Churches with an episcopate that (by our standards) is not in historical succession to the apostles.
Fr. Thomas Kocik criticizes Brown’s proposal on the basis of the position of the Catholic church that “the episcopate in communion with the successor of Peter is divinely instituted and essential to the one Church, which exists in and is formed from the particular churches”. This is, I think the standard response of official Catholic ecclesiology. However, I think that Fr. Brown’s point deserves more consideration. If the monoepiscopate is essential to the church, what are we to say about the many churches in the first century that Brown describes? It does seem that there was a plurality of church forms in the early centuries of the church (indeed as late as the letter of 1 Clement, it seems that the church of Rome itself was ruled by a college of presbyters rather than a single bishop). If this early diversity of church structure falls within the conditions for ecclesiality, why should such diversity now be regarded as necessitating a division?
At the very least it seems prima facie true that if a plurality of church forms and leadership structures was no impediment to intercommunion in the early churches, there is no reason in principle why it must be a point of division today.