I think it would be more simple to begin from the attachmail Zimlet as it would be integrated in the "Add attachment" when composing a new mail.
The new tab in the attachment popup would allow the user to browse within its contacts and select the one he wants to add.
The problem I have with the "contact attachment" zimlet is that you normally attach a vcard in a mail that has already a discussion. Usually you say to someone after a discussion that you attach the contact in the next e-mail so you can keep
However, with this zimlet, it's a complete new mail that is being created and you don't have the discussion.
This zimlet is, in my opinion, a first step to attach a vcard to an e-mail and this is really great that someone tried to solve this missing part of Zimbra
