The trouble is, people think it will be a magic wand that will solve all these problems overnight.
We have separate systems for passports, health services, schooling etc, but they don't talk to each other. Anyone who has dealt with more than one area of the NHS recently will know the frustration this can cause. Some parts of the NHS still use fax machines!
Bringing in an ID card is just a distraction, will cost billions and nothing will change much. ID cards can easily be faked or stolen so it won't do anything to stop illegal immigration.
If that is the aim then it would be more effective to start a biometric database, with ID cards, just for foreign migrants. Students, workers and those who arrive on rubber dinghies, all are recorded on arrival and put on the database. Illegals will likely give false names, but you will have biometric data if they are caught so it doesn't matter. If they are caught out later uskng a different name, that gives a reason to investigate further. Biometric data could be compared with records abroad.
If someone who has been previously deported turns up again, they can be identified and it will cut down appeals and processing time.
If someone is caught working when their student visa has expired, ditto.
If someone is not an asylum seeker but a wanted criminal, not so easy to hide. In fact maybe give Britain a miss.
If someone is not an asylum seeker but just someone from a perfectly safe country who is trying their chances, same thing.
Legal migrants who abide by the terms of their visas will have nothing to fear (isn't that what they keep telling us?) those doing wrong can be more easily traced and dealt with.
This would be far cheaper and more effective way of dealing with the migration problem than setting up a database for a population of 70 million people. DH has worked on many government IT projects, the problems are immense, as is the money wasted.