That will be a great feature. Currently, due to this missing feature, exporting the pdf to online publishing platform like 'issuu.com' is a pain. One has to alter the project after exporting the original for print/blurb, tweak it to move covers and pages, and then export to PDF.
actually it would be even better to just have an export to pdf button inside of lightroom in the book module. i am on pc and have to go the third-party-pdf-printer-route and that leaves me with wrong colors.