We really do need a tool, the like of which I was using 40 years ago
when writing code, that allows patches to be applied independently
that's what pull requests (or gerrit) are about.
and
temporarily to see what it then looks like and if agreed that it looks
good, incorporating them permanently into the source (XML). Ideally
such a tool would reverse engineer the amended text into XML patches as
well - text is so much easier to work with than XML (or any other markup
language).
try writing the draft in markdown and using Miek Gieben's or my tool
(kramdown-rfc2629) to convert into XML.
it is so much easier to collaborate in markdown...
Grüße, Carsten