User might want to delete some resources from the created Archive (e.g. because he doesn't have any control over how it was created in the first place.)
Right now he can only use a String-based path to the resource he want to delete.

It seems to be an API inconsistency as he can Archive.add Package or Class objects, but cannot invoke Archive.delete(Archive) / Archive.delete(Package).

Example: https://gist.github.com/2989390