But the point is that in the RCC, there is a certain mechanical aspect to the whole bestowal of "apostolic succession" on a particular bishop or church that does not exist for the Orthodox. This is why you guys have episcopi vagantes and we do not. Should someone be ordained by a bishop (or for that matter consecrated one) in one of our churches only to later leave the faith in favor of something else, they don't get to take their "validity" with them. My understanding is that once you're out, you're out. You must keep the faith if you are to keep the episcopacy. Otherwise you end up with nothing but pietism in fancy hats and robes.
What do you mean by "...a certain mechanical aspect to the whole bestowal of "apostolic succession"..."?
'Mechanical' meaning that it is a matter of a who ordained who operating separately from keeping the same faith
by which you were ordained. This is how certain people and churches understand apostolic succession: "I was ordained by so-and-so, who was ordained by so-and-so, and because those two guys are 'valid', I am 'valid' even if I'm not in communion with their church (anymore)." That doesn't work in Orthodoxy. You don't retain your status as _____ (whatever was conferred upon you) if you leave the communion. Like in my case, if I were to go back to being under Rome (hypothetically, of course!), I wouldn't be an Orthodox Christian anymore. I don't get to take that with me, so to speak. I didn't become some other thing, ontologically, by virtue of my baptism. So if I leave the Church, I don't become an "Orthodoxe vagante" or whatever -- I become some guy who is out of the church. The end.
episcopi vagantes? I seem to have heard of 1 or 2 vagante "Orthodox" Churches. Milan Synod (or whatever name it goes by now)? Or is that something totally different?
You'll have to ask others about that. I have no idea what you are referring to.