Unfortunately I don’t like the spacing/widths, and it looks like the sort of thing that would be better constructed by a filter or script. Does anyone have a suitable one already? If not, I would be happy to write one but am not quite sure how I could make it work.
If I would implement such a effect I would draw the outmost and innermost shape. Do that in groups of two for each shape (in your example two paths for the outer shape and two for the stroke). The interpolate a few steps between each pair and connect them as needed. To be able to repeatedly run the filter, first put the paths in the background of its empty or use paths from the background if there some. I used the same approach for the hatch filter.
Thanks for the tips. I wrote a script which identifies the start and the end segments, gets the two sets of path between those two segments, and then interpolates various points between them.