Like Google, Facebook, Apple... Make it possible for websites to make a Login with Firefox option available so we have a trusted privacy preserving option given to us (and give Firefox some visibility)
@SergI know it's not best practice but it's better than a weak password or connecting via Facebook/Google, also Firefox has a password manager, getting your Firefox account hacked can already make you lose access to all your accounts. The benefits outweights the drawbacks in my opinion and it expends the Mozilla ecosystem (which in my opinion is missing a big opportunity by not making google alternative services in partnership with other brands but that's an other subject)
I think there's some current thought going into something like this as well. Decentralized identity? Federated identity? Those keywords have been thrown around.
If there's a centralized authority, it seems like you could have it issue as many identities per account as you want. Heck, Firefox Relay already does something like this, splitting one email into multiple. But this is tricky stuff that I don't understand very well, so I dunno.
I like the overall idea of it, it would be interesting if Mozilla brought Persona back. I would trust it and use it over "Sign in with Google/Facebook/ect".