Sounds like you are describing how hardware tokens are typically done? With this being an idea of how to move the token into the cloud?

I can kind of see the reasoning on why the browser wants to do this. Every one of them has a "generate secure password" feature bolted on, now. And I'm not clear that any of them have a way to port passwords out to another source.

Still feels a bit uneasy to me. Physical keys for property provide the kind of security that just doesn't cut it for virtual assets. Such that I'm having a hard time seeing any model without terrible failure cases. :( Super glad that isn't my day job. Good luck to them.