Actually, there's already filesystem I/O in HTML5. I'm not sure what you mean by "privileged Chromium mode". You could very well just use the regular mode that

Actually, there's already filesystem I/O in HTML5. I'm not sure what you mean by "privileged Chromium mode". You could very well just use the regular mode that exists in your browser to create a full-blown application. Of course there's always contraints, because you only have available the HTML5 api, but now days you can do lots of stuff with it - it pretty much has everything a regular app would need (disk IO, network IO, UI, etc.). As far as security goes, the Chromium sandbox is much more secure than any other code you would be writing yourself - after all it's the same thing that runs inside your Chrome browser, which is world-class secure. For the Node instance, I also don't see any issue here. Sure the web-server that is initialized on your local machine is visible across your local network, but you can simply secure it just as you would with any regular web-application.