The security model of TLS is chained to the DNS. What one proves by holding a TLS cert is that one owns a given domain, no more no less (I mean there's EV certs

The security model of TLS is chained to the DNS. What one proves by holding a TLS cert is that one owns a given domain, no more no less (I mean there's EV certs but no one cares about EV certs). You won't ever have that with browser builds because there's nothing like that to tie them to.. (user agent string?). There will be no basis upon which to build trust except for market share, and to gain market share you have to already be trusted. Also, for WEI to work, you need to certify a lot more then just the build of the browser.... You need to certify all of the shared libraries it pulls in (including the userspace graphics libraries), everything that runs in kernel mode, the firmware, and the actual hardware. I would assert that the idea you are proposing is simply not going to happen. There is just no way that anything other than an unmodified build of a big-name browser running on an OS from a big-name vendor gets certified.