Man, the PL-15 doesn't have a second thruster, it only has one solid-fuel rocket thruster.
The difference is that a general solid-fuel rocket thruster can only work once, without interruption in the middle, and can't be ignited again.
The PL-15 is a dual-pulse solid-fuel rocket thruster. Its fuel rod is divided into two parts. After the first section of fuel is finished, the engine will stop working for a period of time, and then re-ignite the second section of fuel. This is the basic working principle of the dual-pulse engine.
Its engine is not confidential, and the technology is completely public. Its core secret is how to ignite the two sections of fuel rods twice without affecting each other.
The J-10 has a nickname in China called "棍子机(stick fighter)". ------ We put wings on an engine and let the pilot ride on the engine, and that's the J-10.
So, your suggestion about PFX is actually another J-10 fighter. So, what is the point of Pakistan studying this?
In the Chinese fighter series:
- Single medium thrust engine fighter = JF-17
- Single high thrust engine fighter = J-10
- Two medium thrust engines fighter = J-35
- Two high thrust engines fighter = J-20
Medium-thrust turbofan engines: WS-21 (WS-13 series), WS-19. Russia Series: RD-33 series
High-thrust turbofan engines: WS-10, WS-15. Russia Series: AL-31 series
If the JF-17 continues to be developed under the name of "JF-17 series" in the future, such as JF-17 PFX, JF-17 Alpha... then its engine will either continue to use the RD-93MA engine or be replaced with the WS-21/WS-19 engine.
If it switches to a high-thrust engine, then it will be completely redesigned. It can no longer continue to be called the "JF-17 series".