This is brilliant. Here a full-fledged solution: the same way every OS supports users, it should support identities attached to the user account (~/.ssh). Upon

This is brilliant. Here a full-fledged solution: the same way every OS supports users, it should support identities attached to the user account (~/.ssh). Upon OS installation / user creation, it would prompt the user to either generate new identity, or import existing one (from a flash drive, from a cloud, etc.). This would be the key pair. And the browser would automatically use this, without any terminal session or any such non-sense. Brilliant, right? No, because user accounts are commonly shared: here, can I check my mail on your computer? Yes, password won again :P