Honourable Sir,
Lead in fighter training is about learning the fundamentals of flying a modern tactical aircraft. Hence primary function of a LIFT (Lead-in fighter trainer) aircraft is to prepare the pilot for the transition from ‘trainee’ pilot to the frontline fighter aircraft which are normally supersonic and with highly sophisticated radar & avionics.
Thus LIFT needs to have supersonic or high subsonic speed with such handling characteristics, instrument systems and radar that the new pilot is at ease with the handling and sophisticated radar & avionics of the 4th/5th generation fighters. Whereas K-8 is not very fast and to the best of my info, has no radar, therefore is at best an intermediate trainer.
Before one can answer your question, one must look at the design & development of the K-8. Even though it was a joint effort, lions’ share of the work was done by the Chinese.
K-8 was designed primarily by the Nanchang Aircraft Corporation with Hongdu Aviation Corporation as the main contractor. Understand the design team included about 20 Pakistanis and over 100 Chinese engineers.
The power plant is the US built Garrett TFE731 turbofan and avionics being Rockwell Collins EFIS (Electronic Flight Control Instrument system.
Thus, Pakistani share was limited to about 20% in airframe design only with propulsion and control systems bought off the shelf from the US. Therefore to expect Pakistan to develop an indigenous LIFT aircraft based on the K-8 experience is highly presumptuous.