Ask HN: Web Dev Toolbar/Firebug "in the cloud"

The past couple of weeks I've found myself wanting a better way to make and save complex changes to a site in the browser. For example, I often use the Web Dev Toolbar to make a prototype of what a redesign/new feature might look like on top of the live site itself. That way someone can actually load it up (WDT has a save and load CSS/HTML feature) and use it in their own browser with the changes made and the site actually working. It seems to me a natural step to make from this workflow would be to save this updated CSS/HTML (and possibly JS) on a server instead of locally, taking advantage of versioning, sharing, etc. So 1) anyone know if something like this already exists and 2) if not, would anybody be interested in having something like it?