As I think may have been mentioned elsewhere, the *only* problem is that
the rpm signatures must match and the signatures are over the
*compressed* rpm.
I would *love* to see deltarpm rebuilding uncompressed rpms, but that
will require storing two signatures per rpm in the metadata (compressed
and uncompressed sha256), and either modifying yum to check the
appropriate one, or deltarpm to change the rpm's signature to the
uncompressed one.
I don't think we want to go down the road of having deltarpm-rebuilt
rpms not having their signature checked at all.