Looks like there are others with the same off line Collaborative document writing. If you took Sakai + RWiki and exposed its services as web services, it would be a short step to integrating a full blown off line Collaborative Document Writing environment.
You would need a client, but taking the RWiki Render engine, and embedding it as an Eclipse Application would generate quite a nice cross platform environment, not Wisiwig, but then for this type of work, wisiwig sometimes gets in the way, just look at Wikipedia for positive proof of what happens without when you sacrifice wisiwig for collaboration.
http://www.quicktopic.com/37/D/bVHWhMLMj74?inline=1
Just a thought.
