It works! The very same tools which can be used for offline processing can also be used online as a service after a little web programming to interact with them. This way, one isn't limited to pre-defined packages, one can also provide processing facilities to others and integrate them with larger online publishing and distribution systems. A very primitive tech demo with only odt2html1 online conversion can be seen here:
http://www.publishing-systems.org
The next task is to set up the entire workflows just like in the offline version and to add more and more web-specific additions.