I'm not sure this is constructive, but it's meant to be helpful.
AFAICT RFC3030 has not been widely adopted in practice. Why, do you think?
I think it's because networks have gotten fast and reliable enough
that 8BITMIME and various ways to encode binary data (qp and base64)
are good enough.
An alternative to what this draft does is to define some new MIME
multipart types and wrap everything in a new message. That has the
disadvantage that it's ugly, but the advantage that MTAs including
relays don't need to know about it and it's arguably* faster.
So I think it would work fine if people implemented it, but unless
there's a very concrete use case and people ready write and deploy
those implementations, I wouldn't bother.
* - arguably due to more round trips for more commands, arguably
mitigated by pipelining
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