Subject line

It is obvious that descriptive email Subject lines can offer a potential
security leak, aiding traffic analysis and eavesdropping.  Therefore
cautious crypto emailers either leave this line blank, use a
non-descriptive header line, etc.

Might it be possible to add a feature to the PGP cyphertext body so email
plug-ins could save the Subject line in the cyphertext, blank the email
field during transit and restore its value after decryption at the
receiptient end?

--Steve