That's why we need biometric hardware everywhere and use its data as a login, not as a password. Bio data is mapped onto a long UUID and user just sets whatever username he wants to be displayed. We even have means to smoothly transition from no hardware to 100% coverage - just allow manual UUID input for systems where biometric is unavailable - e.g. you have a pair of face/ID on the phone, fingerprint/ID on laptop and just ID on PC.
You keep your UUID as a backup. The fingerprint system on my phone still has an option to log in with password, the fingerprint is just a convenient, faster alternative. It's the same here, you keep the UUID in a folder with other sensitive documents and when you lose your finger, you fish it out, log in with it, and register another finger.
You'll have to remember multiple UUIDs, one per service. Now that I think of it will be rather cumbersome. And bio data has to be editable if it will be usable at all i.e. add/delete new entries - fingers, eyes etc. Damn, it is harder than it seems. Anyway, bio data as a login should be implemented, we only need to think exactly how.
How? UUID will be different per service. Anyway - it won't be worse than current single (2-3) email as a login to everywhere, of facebookID as login to everywhere.
