Hi, I personally am not to thrilled with buying sanction prone F-16s. I personally would not buy these F-16s, but rather use the money towards the economy and try to speed up the JF-17 process.
However, the JF-17 Block 2 is still in its teething stages and the FC-20 is still a rumor. In addition, the PAF cannot afford any European platform, Europe would probably not sell a fighter jet to the PAF, and Russia does not do offensive weapons business with Pakistan.
If you look at the current inventory of the PAF it is pretty week: old F-16s, souped up 60s era Mirage III/Vs, and 70's era Mig-21 clones. The JF-17 is still maturing and has long way to go. Moreover, the next 50 batch of JF-17s will take 2-3 years to build and induct. Also the PAF is only now starting to learn and induct the SD-10a/b BVR missile. These F-16 planes can be used in the FATA region to more accurately target terrorist camps, and also have top notch night time attack capabilites for the WoT (War on Terror).
Mr. MK has correctly mentioned, buying a new platform, training ground crews, training aircrews, and building up a logistics network/system takes many years, As such, the PAF really has no other options that this in the short term. The PAF is fully trained on the F-16 and has a ready maintenance network for this platform. However, I would not recommend buying any more of these planes, and I would use them around the clock and get very cent out of them.