I really like this idea and will try to implement it. Some discussion might help me:
Would it be acceptable to mimic the nosy-email format? That means fields below
message, after a '----------'.
Regardless of fields placement, should there be a marker/tag to explicitly
delimit commands? I ask that because, e.g., your original message could trigger
this behavior when you only wanted to discuss it.
Should the attribute-setting part be stripped from the message?
Should setting attributes both in subject and in body be allowed in a given message?