Just thinking aloud here.
If they are able to integrate PL-12 and PL-8, it would imply they have access to the radar software source code. Wouldn't that basically make the limitations related more to the hardware itself (PL-15 range greater than the usable radar detection range), and/or user interface, rather than technical capability?
Similarly, the Su-27 (original tranche from Russia) was upgraded to fire R-77. The rumor was that Ukrainian engineers with the source code were hired to do this work, is this still the story? Or is there a more concrete story now?