I strongly suspect, given the way the discussion is going, that we
either have to consider framing everything - and that's a huge break
from XMPP - or else we need an escape mechanism that works. Or, of
course, we decide to give up and frame using XML as now, and use
base64 to cope.
Personally I think it would be better to do as someone already suggested
and have a separate connection for framed blobs that you maintain or
establish when needed to send those, sort of like XEP-0065, or why not
just use XEP-0065 itself??, and if the server you are using doesn't have
a XEP-0065 proxy then you can safely assume that the server
administrators don't want you sending lots of data through their server
infrastructure.
Richard