Comment by vidarh

You don't need a national ID card scheme to do this, though.

The EU/EEA is rolling out a digital identity mechanism with interoperable wallets that can hold any range of identity documents and other credentials. You don't need to pick a single wallet provider - several EU countries are approving multiple, including private providers. You don't need to standardise on a single ID.

This is already the case for many already in-use ID solutions in Europe. E.g. in Norway, there are at least 3 signing providers, and only one provider is government issued - the by far most popular (BankID) is private. You identify yourself to the provider when requesting issuance, not to the government (unless you sign up with a government provider).