What I had in mind was more like randomly generated addresses as needed, all of them linked to your (one) mailbox. Like Apple's "Hide My Email", but without needing a "main"/"canonical" email address because it would be unnecessary anyway (because you would be logging in to your mailbox with your own certificate).

But even if that single-address limitation were the case, the kind of places I would give it to already require knowing my national ID number anyway, so the two particular things you mention are already the status quo.

In other words, stuff that is already tied to having a verifiable citizenship.