First, I would like to say thank you for posting your informative studies.
I currently attend a church that has dissolved the eldership and have been operating without elders. After reading Keith Sharp's article on Autonomy I still have a question of elders. Our biblical example is one church in one city with one eldership. The closest thing I can find to many churches in close proximity are the house churches on the island of Crete. My question is why can't a church in the city I live appoint elders to the church I attend? Also, if we operated as the early church, couldn't each city have elders over the churches in that city operating as a collective like the church at Jerusalem? While each church remains autonomous with elders that work together to keep the churches of that city sound. From what you state it leads to denominationalism, but if we are operating without elders then what is the difference? Please help me understand this better. Why we can't have multiple meeting places but one church from one city autonomous from the church in another city? I know that elders talk to one another and gather advice from each other but could an eldership of all the churches in one town work together to shepherd the people of that group of people that meet together but at separate places believe the same things and have the same goals but don't share the same building?
It is true that when the church was starting out there tended to be one church per community. Communities in those days tended to be smaller than today. For example, we know there was a church in Colossae, Heirapolis, and Laodicea, yet these towns were only a few miles apart. But you made a leap from there and assume that cities like Jerusalem had multiples churches, yet there all indications is that it was just one church. There is no passage indicating a collective operation within a city among multiple churches.
"When they had appointed elders for them in every church, having prayed with fasting, they commended them to the Lord in whom they had believed" (Acts 14:23). Each church had an eldership. Notice how you switch between talking about a church in a city and churches in a city. There is no passage that a set of churches in a city can have a citywide church over them.
Having a citywide church operating multiple small churches so adds another organization. Local churches are composed of Christians meeting together in a location. Paul spoke of "when you come together as a church" (I Corinthians 11:18). Christians meeting in different locations are not coming together as a single church. That is one of the reason the concept of "house churches" operating under a larger church is wrong.
The concept of a citywide church operating multiple small churches changes the membership from Christians to churches. This is the denominational view of the church. They see the church as a hierarchy of churches with members only at the lowest levels. This is not the view presented in the Scriptures. Whether we talk about the church as a whole or in a location, it is always composed of Christians.
Elders are to "shepherd the flock of God among you" (I Peter 5:2). There is a direct interaction between those overseeing a work and the members being overseen. A citywide church over smaller churches puts in an additional layer not indicated in God's plan.