I don't know if a personal ID could be added to the Bitcoin protocol. It would be powerful if both personal IDs and ordinary Bitcoin addresses could be used. I would then store most if not all of my bitcoins (if I had any) with my personal ID so that they would be secure automatically. Another person may want to do the opposite and store most of his or her bitcoins with Bitcoin addresses and only a few if any bitcoins with the personal ID. That allows maximum personal freedom and flexibility.
The problems starts when your "personal ID" gets compromised.
Biometrics and things like that are probably needed. So I admit that it's a tricky and big problem to solve.
Biometric is unfortunate not deterministic, since the human biology is not constant. Therefor is poorly suited for decryption or message signing. Perhaps 10-15 years from now, but the technology and infrastructure is not ready in its current state.