IMAP extension for SASL additional information

Do IMAP support SASL authentication where the server returns additional
information together with success?  As far as I can tell from section
6.2.2 of RFC 3501 it does not, but I may be missing something.

Is there interest in an extension, say "SASL-AD", to provide this
capability?

It could work like this:

C: . CAPABILITY
S: * CAPABILITY SASL-AD
C: . AUTHENTICATE SCRAM-SHA-1 - SASL-AD
S: + 
C: client-first-b64-string
S: + server-first-b64-string
C: client-final-b64-string
S: . OK [SASL-AD server-final-b64-string]

When used together with SASL-IR, an exchange could look like:

C: . CAPABILITY
S: * CAPABILITY SASL-IR SASL-AD
C: . AUTHENTICATE SCRAM-SHA-1 client-first-b64-string SASL-AD
S: + server-first-b64-string
C: client-final-b64-string
S: . OK [SASL-AD server-final-b64-string]

Using "-" allows clients to avoid sending a client-first even if the
server announces support for SASL-IR, thus enabling: