I was trying to figure out some more on the Burnham Brothers and their not being on the Angel Gabriel. There is a list of proprietors of Ipswich (called commoners in the text) dated 28 February 1641/42. There are 111 names on this list. No Burnhams. That says something. Of the people on the list, I descend from several including Regnald Foster, John Perkins, and Moses Pengry.
I suspect that if you wanted to speculate on other passengers on the Angel Gabriel, I would see who else was made a freeman from Ipswich at the same time as John Cogswell. Then I would see if any of those persons left any records prior that. If not, that would be a start for a speculative list. It is common that people from the same ship tended (at least at first) to live in the same community. That's another reason that the Burnhams were put on board. The Ipswich connection.