"There are number of ways howto 'debug' chip using power consumption, xrays etc..."

The circuit on the chip is known, that's not important. The important thing is the information in rom. Difficult, but certainly not readable through x-ray.

"It is easy to copy GSM SIM card. Also operators usually give replacement SIM"

Of course they can give you a replacement SIM, they can reconfigure their systems to point the customer to the new SIM. That's not copying.

Actual copying would be more difficult.