I (as have many others) considered building something like this in the past. What you say was exactly what put me off. The difference in CPU time between downl

I (as have many others) considered building something like this in the past. What you say was exactly what put me off. The difference in CPU time between downloading a page and rendering it (even virtually as with say PhantomJS) was sufficiently large that running in the browser (not centrally) seemed to be the only general purpose way and maintaining _browser_ extensions is... a pretty major job. I was looking into writing a daemon to externally monitor the browser and it's cache (such as Chrome's Current Session file) when I left off. Hopefully the use of server-side prerendering will catch on, be it through Node or other systems...