From Wikipedia, this is JL-8
Whereas this is labeled as an early variant of L-15
and this if what it finally became
Notice in the second picture the nose is still conical, but the position of the wings and air intakes has been changed. Then finally, the nose has become more angular.
Why am I calling this the next iteration? Because, this is what wikipedia has to say about FTC-2000
In the same sense, I see elements of JL-8 in the airframe of JL-10. Similarly, regarding the powerpack:
Again, the powerplant is from the same Ukranian company. If you want to disagree, its your right. But I have explained my reasons.
What is your criterion for old and unreliable? MRF has the facility for complete MRO of the engine. In effect, it can recreate the engine as brand new today. Mirages have been one of the most reliable platform in PAF. The SNECMA afterburning engine would provide cadets with a very wide range of power profiles to learn. There is every reason to leverage existing expertise to cut down costs. It seems stupid to you because maybe you don't understand the extent of PAC's capabilities.
Of course it would be a new aircraft structurally. But by sharing avionics, weapons, and ammunition, and overall external design, it should cut down costs. There are examples of such projects around the world. The Japanese modified the F-16 to essentially make a larger variant.
How is it worse than FTC-2000? Aircraft aren't lego, and I haven't proposed anything that has no parallel in the rest of the world.