in my opinion, in any case Pakistan will never go for FC-31 instead they are planing to develop their own single engine stealthy aircraft, which could be based upon the the experience of JF-17 and it would be a mixture of chines, Turkish and russian avionics, and this approach seems more logical when we keep in mined the followings:
1... design and development of a new fifth gen aircraft from scratch, requires a knowledge base and previous experience, infrastructure backed by sufficient budget
2... while state of economy is not suitable to spare a huge amount for research work in near future.
3.... Pakistan airforce has a long experience of single engine fighters jets, which mean training cost of manpower would be less.
4... maintenance and operative cost of a single engine aircraft is less ..
5... in that case shenyang which is developing FC-31 would be willing to invest in the development of this new aircraft keeping in mind PAF would be a confirmed customer. even i am expecting TAI too because such type of aircraft could be a hot cake for developing world countries... etc.. so the design could be something similar to this...