Well said. As I said, I don't link to the Internet, even to Ancestry. I make sure to have a local copy of every source I use. While in the old days that meant reams of photocopies, today it's as easy as downloading a census image from Ancestry and attaching a copy to the source citation in FTM, so why wouldn't you do that?
While I agree with the first two of your principles in theory, if I rejected every source that didn't adhere absolutely to "exacting standards", progress would be really slow. I have more than once found less exacting sources that were nonetheless of value; though I do usually make a note to that effect in the footnote.
As to the third criterion: if I've collected every source my source has cited, why wouldn't I just cite them directly?