There is only one way to lower memory usage IMHO:
to display dump statements one by one. It means that
we should stop output buffering while building dump
(easy to do) and create a temporary text file on the
server that will contain the dump statements before to be
compressed if compression mode is required.
It means we have to setup a directory that is readable
and writable by the script where to put these temporary
files.
What you think about crete a phpMyAdmin database and use that for
temporary data. This also can hold configuration variables, query bookmarks
and translation strings.
Loïc
Saludos Edu