Not getting 404s is quite a problem with my project - I've mentioned before, I'm trying to write a mediawiki presentation layer client-side reimplementation, as an experiment into very low spec web servers. I'm giving a presentation on Monday and will probably post a link to my work shortly after.
Sounds a lot like an idea I had and was planning to implement in some time. So is it pure JS with XMLHTTPRequest that you're using for this presentation layer? I have a somehow working MediaWiki-to-HTML converter written in JS which I'm using for client-side previews in edit pages. Have you implemented something like this as well? If you think it could be useful for your project please let me know. I'm very intrigued about your work.
Pedro