Exclusive Brethren - Elders an Impossibility?

I was doing some surfing on the BrethrenPedia website, when I ran across this piece of information (in the boldface print) that I had never heard before:

"As the name implies the Exclusives are so named for their practice of serving the Lord's Supper exclusively to those who are part of their own particular group, agreeing with them on various doctrinal positions.

Most exclusive groups believe the church to have been in ruins between the death of the apostles and their own time. Since no truly apostolic authority exists to appoint elders the church has none. Instead they recognize leading brothers who demonstrate maturity and leadership ability."

For a few years I've thought it would be interesting to do a study of Darby (from whom the Exclusives, moreso than the Open Brethren, trace their roots) and to consider what things might have carried over from Darby's Church of Ireland (Episcopal) background into the Plymouth Brethren. And here's one example. The doctrine of the Apostolic Succession of ministers is not exactly the type of thing most who are familiar with the Brethren would expect to find taught among them. And it seems that this would contradict their concept of there being no distinction between clergy and laity, as expressed in the same article:

"The most defining element of these churches is the total rejection of the concept of clergy. Rather, in keeping with the doctrine of the Priesthood of the Believer, they view all Christians as being ordained by God to serve and are therefore ministers. Leadership is by example and by the recognition of their abilities by those they lead."

I wonder what they believe would have been necessary in order for the succession to have been continued. I was taught among the Open Brethren that while there were certainly believers through the years since the time of the apostles, the church was still in a ruinous state. But it's hard to figure out exactly what they thought would have had to be in place for the church to not have entered that state. The impression I got was that the church would have had to maintain the "Assembly Distinctions", which included things like no clergy/laity distinction, no salaried ministry, women wearing headcoverings during assembly meetings, a specific approach to worship, no women leading in worship or otherwise teaching men, local church autonomy, etc. But why would doctrinal and practical purity have been necessary to maintain the lineage? There seems to be a strong concept of Perfectionism here, which would explain why the Brethren began separating from each other almost as soon as they met and began fellowshipping together.

One other thing that the average Assembly person probably doesn't know is that Darby never rejected infant baptism, unlike most of the other founding Brethren. This has continued among the Exclusive Brethren to some extent. Here's what it says in the BrethrenPedia article on Baptism:

"Since their beginning, the Assemblies have practiced two modes of baptism: Believer's Baptism and Household Baptism. Believer's Baptism is the baptizing of believing adults, and is always performed by immersion. All Open Assemblies and some Exclusive Assemblies (in the USA) practice Believer's Baptism. Household Baptism is generally baptism by immersion; it includes infant baptism either by immersion or sprinkling. Some Exclusive Assemblies practice Household Baptism."

Interesting.