That’s actually brilliant, and easily replicable in BibDesk with a custom html output template.
Here’s an AppleScript that creates html, one file per publication, ready for import. As written it uses the default html template which isn’t ideal but easy to customise.
set loc to "/path/to/folder/"
tell application "BibDesk"
set s to selection of document 1
repeat with i in s
export document 1 using template "Default HTML template" for i to POSIX file (loc & ((cite key of i) as string) & ".html")
end repeat
end tell