I mean has anyone written a book on just sword suspensions?

I'm not aware of one. You can find information in the great books on swords, but I'm not aware of so much as a chapter or chapter sub-head on the subject. Depending on your interests, you'll find clues in Oakeshott and Neumann (Swords and Blades of the American Revolution). Artwork from your period of interest is probably the best primary source of information. As a secondary source, just search this site for well-researched interpretations.

I ended up doing my own research folders, of photocopies of photos of extant scabbards and suspension systems, and it quickly made me appreciate the huge variety of methods and decorative possibilities. I've never heard of a book devoted to the subject though.

Anyone interested in writing a feature article? This subject comes up often, yet there's no single published resource.

Sean, please offer fame & fortune. Well, at least long lasting fame would result. :) & seriously. A feature article even just generally outlining the main suspension & attachment methods would be great.

How about extreme gratitude and the personal satisfaction of serving fellow arms and armour students? :D

By the way, I checked Claude Blair's European Weapons last night. He has a few paragraphs on the subject, but I think most of us would consider it elementary.