Came across this thread these many years later. I heard Graham sing the song at a British folk club (no idea which one any more) and learned it off his and Eileen's record. I don't recall sitting down and consciously changing any of the lyrics, but in performance it's pretty typical that a singer will gravitate to slightly alterations that feel more natural. That certainly explains the alterations marked above as "for scansion".
I personally will not be adding Bob Rodriguez's verses. While they're nicely done, I don't think they are in keeping with the rest of the song, which focuses on the minstrel's role throughout these various stages of (English) history. Rodriguez's verses seem to me to be about the events *around* the minstreal, a real difference. (Also, at least one of the verses is presumably fictional, and for me that also does not fit the point of the song.)
The MP3 of my recorded version is still available at the link above.