Re: ID Card
Most National ID cards that I have personally seen and I have seen most of them from the EU, don't even have the bearer's home address on it.
I would never want my proof of identity device to have my address on it. Otherwise every time you change address you need a new device. As someone who rents a flat, I've changed address four times in seven years. I replaced my drivers licence once, when I moved most recently, and then only because I lost the paper part of my licence.
A better question would be why opening a bank account requires proof of residence at all. Proof of identity, sure. But an address is a pointless exercise now that you are no longer associated with a specific branch for your services. Not to mention the trap it puts on poor people, who often have no fixed abode, but can't get one because they can't get bank accounts, et cetera.
Replacing disparate numbering systems, NHS, Driving licence, National Insurance, to name but a few, would be a large and costly undertaking at a time when most government departments are having their budgets slashed.
I think you missed the part about all government services being required to work together. Each can retain their own systems, identifiers and databases, they don't even need to alter anything internally. Each would simply need to provide an open EDI interface that the secured middleware layer can communicate with. The middleware layer handles the translation between departments. So you start with something straightforward, like the driving licence system. The middleware layer associates the pre-existing drivers licence number with the ID number you have created for the relevant individual and boom, they know they are talking about the same person. You can then add other government departments one at a time and confirm the interoperability. So your principle expense initially is in the middleware layer. Each additional service added is cheaper and cheaper, as the underlying platform is already there.