This is for ePubs,
- I move any blurb from calibre's Comments (dc: description) to a custom element called blurb/Blurb.
- I strip all non-dc elements and the cover with the calibre Modify plugin
- I insert a full metadata jacket that includes some of my custom columns at the back of the book using a plugin I hacked out of an old version of Modify.
Good luck with your project. Maybe when its done you could post your findings, I assume this isn't your sole source of information.
BR