I was working on this but stopped a few weeks ago.
I'm no expert but it seems that the project-manager is based on the content-repository. I could not find any 'package_id' parameter in any of the pm_* tables.
One possible way may be to subtype the cr_items table with a 'pm_item' object_type and have a 'package_id' item parameter much like cr_folders.
This would allow multiple packages and each project to map to a particular package. Also a package may have multiple projects.