The system you are describing exists already, in China. And indeed it "makes many, many things possible". For one, it makes the concept of a ticket meaningless: either your "single living organism" (i.e. biometric ID) has permission to enter the movie theater, or get on the train, or whatever, or it doesn't. The hassle reduction is enormous! And it is also widely considered dystopian.

Clearly the crucial issue is the "untraceability" of the ID. In practice somebody is going to have to know who is who, and in practice the state is going to arrogate that role, as perhaps it should. So the fundamental question is whether it is possible to make the state democratically accountable.