How can I get JavaScript to read server HTML and build objects off of it?

afaict, you can't do what you're trying to do. You have annotate the HTML somehow to indicate where the bindings were, reverse-engineer the data out of the rendered template, and build a proper template from that so that you can then use an off-the-shelf js templating engine. You might as well just use standard handlebars and web services instead.

If the extra http request from the web service is a real concern (and not just premature optimization), then you could dump the JSON data into a script tag and send that together with the template.