IMHO, some of the major areas for a basic jet manufacturing are;
1) Design----> i think pakistan has good know how as far as the design is concerned because it has provided very valuable inputs in the aircraft designs and made changes to alot of chinese fighter jets that it procured e.g F 7 , JF 17(Joint Venture) and J10 .
2) Avionics---> i think pakistan, if not capable of fully manufacturing, is in good understanding of the science and mechanics of Avionics, we have produced/improved some good stuff in collaboration with friendly countries and i personally know some people who worked on such projects with success.
3) metallurgical science---> we do have reasonable knowledge of it, however, we desperately need to aquire advance knowledge and tech in this area.
4) Engine ---> we desperately need to research into this area with full thrust, if u know and can produce the metals to be used in the airframe, u know the avionics and control systems then the only thing u need to make that piece of metal airbourne is the engine, the engine will determine the scope of the jet, its speed, weight lifting power, range(fuel efficiency), overall cost of jet, endurance in the air etc.
keep in mind that i,ve only mentioned major areas of a basic jet not the advance techs available today and i think there is no harm if the SAARC countries start a joint aviation and design university for civil and commercial use initially on the format of EU which may help them produce some good stuff which would be viable ofcourse coz they themselves are the biggest potential market for such products.
FEEL FREE TO DISAGREE....MY 2 CENTS...