Well There isent any realistic reason for China to operate few F-16. They would only suffer from same proplems that forces Venezuela to consider their sale. Hower, I wouldnt be so arrogant and declare that China dont need them as technology demonstrators, cos they are old block version. They still are potent four generation fighters and Lot could be learned from them. Thought some of Chinese possible opponent operates newer models of F-16, they still share some of the key elements of their follow ups and could be used to simulate Taiwanese, Korean and Japanese air element in similar manner that NATO has used german MiG-29s. Their service life wouldnt be long hower, couse we cannot just assume that Pakistan would defy US so stubidly by retransfering some of their own F-16 components to china. Also, it would be economically too expensive to reserve engineer totally differnt technology to few dozen aircrafts.
Thougth there is also the possipiliy to try to reverse engineer some of their technology into new chinese technology, like the F-100 engine and radar system.