Probably need to also find a way to stage dummy content as well. Would perhaps need to setup a JSON config file pointing to files within a content subfolder. Could get complex, but will probably be necessary.
Also need to decide if this can be done with just Sinatra or if Rails would be advantageous. (I'm guessing that Sinatra will be sufficient though.)
Suggested path for designers: create a style guide involving most or all content templates.