Recommend we create a new MimeType for Atom feeds
Could we say a new MimeType for Atom and its application to archiving, editing and syndication?
No need, those are usages, not different types. Different application/atom+xml entities may have different XML document types (<feed>, <entry>, <archive>), but even then some may be "sent" or "retrieved" in different use-case scenarios.
Has anyone attempeted to get this registered with IANA?
Let's agree, then someone volunteer to write up an RFC for it.
If the format is called "atom", and it's in XML, and unless you have a reason for flying in the face of RFC3023, then application/atom+xml is the only sensible choice for a name. Someone take up the cudgels.