"some chanteys are far more likely than others to stick to a standard development."

Agreed.

And I can see items that may have developed semi-standard forms (i.e. before revival) -- but my emphasis would be that they developed as such, among certain groups of singers, after a point. So, if the question is of of dating the items, I wouldn't know where to draw the line between when the item was sung in more open-ended fashion and when some "closed" form became popular with some people.

I think Reuben Ranzo was a "cultural trope" or whatever, like Sally Brown and Shenandoah. Evoke the Name, and your mind typically goes to singing verses related to the theme of this legend.

I think "Hanging Johnny" suggests the technique of creating verses related to hanging. "Cape Cod Girls" is a "technique," too, more so than a song. You can pull out the "technique" of creating a bunch of verses related to "girls of this and that place." I suppose someone did that while in the midst of singing the "South Australia" item, and then it got "locked in" as an item in itself, through the collecting/publishing process.

I suspect "Blow the Man Down" didn't originate with any/strong theme, but that it was popularized with narratives texts.

So, I'm thinking of a few different phenomena for creating verse lyrics.

1. Verses with no fixity whatsoever and no attempt to relate them to the base-form (chorus). These may, in the moment, develop into #3 below.

2. Verses that one sings, not exactly, but with some consistency due to being inspired by a general field evoked by the chorus subject (the legend of Sally Brown) or some tasty word (e.g. "blow", "hang").

3. Verses that cohere with each other -- but not necessarily with the base-form -- because they follow a technique. The mind of the improvisor goes to a formula like "X girls are ABC" or "Was you ever in XYZ", and then s/he decides to spin out subsequent verses on that formula.

4. Narrative texts that, perhaps out of boredom with a much-used base form, perhaps to satisfy the aesthetic preferences of a particular culturally-oriented group of singers, are "spliced" (Hugill's idea) onto the framework of the base-form.

What is relevant about "John Kanaka," with what little little information we have, is that aside from the chorus phrase of "Kanaka" -- if it really is the Polynesian word -- there is nothing to suggest Polynesian stuff. And the verses we have from Hugill don't strike *me* as forming any particular theme. They'd be just as at home in any other performance of the majority of chanties without standardized themes. (#1, though possibly #2 if we had more info.) So, reading the Hugill verses against a background of imagining the song as a Polynesian-themed thing is, in my thinking, a big mistake.