IMO ... for a 'JF-17 NG' to be a success, it would basically have to be a redesign of the JF-17.
The current JF-17 is a compromised solution by design so as to save costs (e.g., stable design, limited range and payload, etc). It's a semi-modern solution in that it delivers the right electronics and weapons, but for it carry next-generation needs, it'd need a lot of reworking.
This could basically be a project in the vein of the Tejas Mk2 and Gripen E/F.
IMO, a workable alternative is to call a moratorium on any further JF-17 design work, but instead, extend the production run to 250-300 using the JF-17B and Block-III combination. Let's freeze any further work and start saving money via economies-of-scale and a reduced development overhead.
In tandem, we can venture into a joint-project for a twin-engine NGFA (e.g., TFX) and, in parallel, start actual studies on an eventual JF-17 replacement. The cool thing about the TFX is that it presents us an opportunity to ride shotgun with the Turks and basically learn the fighter development process.
We can re-apply those learnings to our own indigenous single-engine NGFA (which we can slate for a 2040 or later timeframe by developing the inputs on our own, albeit slowly). If we co-invest in the inputs, we can also re-use some of the TFX stuff, e.g., TR Motor engines.
