PAF is in no rush with new unproven platforms from China right now. China will have to create a full weapons system and platform and the full eco-system around the J-35 before PAF will consider it. Pakistan wants a "mature and debugged platform", it does not want to spend billions of dollars in getting the chinese to develop the IP and tech for the J-35 and have nothing left to buy the damn thing if that is what PAF intends.J31 is not ready for anyone to realistically get it. It would require further investment to convert prototype to a functioning platform.. PAF has been playing the waiting game with the Chinese to let them invest the money before it will say YES or NO. The Chinese till now have not blinked which is the reason why there has been no progress beyond the 2(possibly 3) prototypes.
The problem is estimating what the sunk costs are likely to be and how it would impact on the prospective local programmes. The other issue is the engine for a fifth generation platform. There is no engine in China yet which would power this platform. So we may have a platform but no engine. So how does one run with such a platform. RD93s which are currently being use for the prototypes are not suitable for such a venture.
Pakistan can look to TFX, and maybe even KFX Block II as options for an off-the-shelf product while it attempts to progress Azm...
PAF has learnt alot with the JF17 programme where it was left holding the baby (ie funding the full development of JF17 itself, after PLAAF walked away) and it won't make the same mistake again with any chinese platform. It takes serious amounts of time and money to develop these platforms into something useable.
VT4 is a mature platform. Type 54 is a mature platform .. etc..