For [11]: I think it makes sense to also highlight other approaches than OpenID such as https://passwordless.net which is a sort of way in the middle (disclaimer: I'm the author)
Persona is just a protocol though, it's implicitly supported by all browsers. Though in-browser auth (which is the ideal case) is only in Firefox so far...
> JS requirement
Granted. Though theoretically, you don't need javascript.
> reliance on email
Granted again, but this is a completely acceptable tradeoff for 99% of services which will require an email and usually even use it as the user's identification.
Still not sold, but I'll keep your solution in mind. Thanks for alternatives! :)