What about a chromiumOS based OS instead?

Taking a look at fydeOS it's clear an identity service based OS is quite easy to implement. Making access to an online account located on EU servers, and considering 99% applications used in the public sector are webbased, it would be an headache free approach for workers.

Any LDAP server could be used, most governments have theirs already, it would be just a question of creating plug modules for each country.