Oversight definitely has the potential to protect against charlatans. But "who watches the watchmen" has always been a problem in Christianity. Because the new testament doesn't lay out a clear structure of government.
Maybe the most senior bishops could periodically come together and vote for a head bishop? who would preside over a system of rules to keep bishops themselves in line and the protection of doctrine and practice. Well.. that's Catholicism.
Well maybe if you don't agree with Catholicism then each church should follow its own conscience? Well now you're no further on than where you started.
Maybe there should be some sort of connection to the apostolic tradition? Or the brushing away of tradition and reliance only on scripture?
But the new testament itself is no help in this regard. By all accounts Jesus appointed 12 rulers of the church age (I use that word because he says they'll be seated on 12 thrones ruling in Mat 19:28). And appears to have appointed a 'leader of leaders' in the form of Peter in Mat 16:18-19.
BUT! Despite all this apostolic hierarchy being laid out all nice and neat God apparently goes and appoints a man who never met Jesus in the flesh, Paul, to not only be an apostle too, but such an important one that he writes the larger part of Christian doctrine.
What on earth can we make of that?
Is the age of apostles over? The Bible doesn't say it is. Must an apostle be subservient to existing apostles? Paul wasn't. He avoided Jerusalem for years, and finding they agreed on the gospel they agreed to go their separate ways. He said titles don't matter and who or what the original apostles were didn't really matter to him (Gal 2:6). And if one can even find some sort of mutual recognition in these verses it didn't stop Paul, this outsider, opposing Peter to his face, and in public, over a matter of doctrine! (Gal 2:11-13).
So much for submitting to your bishop..
I only say all this to point out the Bible is a terrible example of how to try and have a hierarchy of authority to keep things in order. Whatever structure we might think Jesus put in place gets usurped shortly after by a guy with no better claim to authority than "he had a vision" and "really believes what he says".
Which is all to say that unfortunately St Paul possibly originally came across like the myriad of modern wingnuts who run all sorts of odd churches contrary to tradition or ecclesiastical authority.
The only thing I think can be salvaged by Christians from the new testament is the acknowledgement that ultimately "you'll know a tree by its fruit". There isn't really any restriction on someone setting up a new church with different rules and beliefs just because they think God told them so. Even if you think those rules are exploitative or unfair or wrong.
Even Anglicanism came about this way.
Ultimately I think the dearth of information on how to structure the church in the bible is, if anything, completely deliberate. If God wanted to give a plan of how this was supposed to work for all ages he could have given some thoroughly detailed information on it like when described the tabernacle, priesthood and rituals in excruciating detail for 5 whole chapters (Ex 26-30)
So I'm suspicious of highly developed ecclesiology. It looks useful on the one hand. But, being man made, has led to abuses of power just as bad as the charismatic charlatan preachers out there on their own.
The response to this can only be to teach Christians on an individual level to be skeptical of power and to protect themselves from those who would use their spiritual 'authority' to coerse.
How anything collaborative and organised could possibly arise out of that would then truly be a miracle. Maybe that's the point.