write native code, and have it run on all platforms that have a browser. Even if it’s possible or not, to utilize gpu cores, you could still harness, many many many render machines by just posting a link on facebook to friends collegues etc.
and have their machines help you render future blender projects.
even having blogs, tweets etc to gather people to hlep you render could gather up a huge amount of render machines.
and best thing would be OFF SITE managing render machines by just posting a URL to a render machine.
and it runs the renderer in browser which networks renders the image.