[voyou]

> What you want can't really be achieved without something on the server-side (rewrite rules with Apache, routes with Rails)

That's true, but the rewrite rule could be very simple. Have all pages of the form http://site.example/* serve up the entry page (which then uses JS to parse the URI and load the appropriate page content), and special case http://site.example/pages-directory/* or something to serve the content for specific pages.