For region hacking they'll have to hack the 360 motherboard rather than the DVD drive. Region coding will be carried by the XEX files (which are signed). Even if the DVD drive could intercept XEX files and change their region, this would break the signature.
How feasible this is depends on how the 360 stores its region info. In the case of the original Xbox this was on the EEPROM, so a PIC could have been used to rewrite the region code, had the whole system not been blown wide open first