I agree that only the national regs should be allowed in each country. Otherwise it becomes unworkable.
One example is the difference in earthing systems. Denmark uses mostly TT since the neutral in the network isn't properly earthed, while Sweden only allows TN and doesn't require an earth electrode. Danish electricians working in Sweden have managed to set up systems without working earth. I'd be surprised if Swedish electricans haven't made the opposite mistake in Denmark.
The only other code that would do would be European Wiring Regulations written specifically to be applicable to all member countries. It would be a rather thick book with national deviations, comments and warnings. I don't think it is a workable idea in the near future.
