It would depend on the device. In general, all devices that can be easily modified are Qualcomm Snapdragon devices. This is because their radio is software controlled and their radio firmware image format is well known. So you can even cross flash some radios with no modification (I believe the HTC One X and HTC One S are a good example).
Beware thought, it doesn't mean it will work well. The Note (i717) has severe data speed issues after a reboot and some radios have severe voice quality issues. So its not a good idea to buy a phone just to modify it.