It would be impossible for most phones, but not the S3.
The NFC antenna is normally part of the back of the case, so you couldn't have a clear case. The S3 is totally weird because the NFC antenna is part of the battery.
In fact, that's why you can't really purchase a battery on eBay for this phone, if you want NFC. Even the batteries marked OEM are mostly fakes, and the counterfeiters aren't including the NFC antenna in the battery.