Hi!

 I think a warning would be convenient when the package hints through
its version number (or changelog history?) that it is the first upload
to the pool but does _not_ include all parts referenced in the dsc file
(i.e., missing orig tarball(s)).

 This could/should especially also check for first uploads to
backports where dpkg-genchanges doesn't (yet) automatically include the
orig tarball(s), to avoid these issues.

 Thanks,
Rhonda