This was actually my point! Some sort of access other than an imap: or
ftp:
access to the raw message/rfc822 is what most of us would like to get.
Well, if the IMAP archive were organized so that all of the messages
sent to one list were in the same folder, the URI would actually serve
as a pointer to not only the message, but the location of the message
within the list archive. And from there (especially with a threads
extension) the MUA could presumably look for other messages in the same
thread.