I believe that someone somewhere in LM is smart, and that any obvious, low cost, no tradeoff improvements to the F-35 that are so obvious an internet discussion forum can think of them have also been considered by professionals.
I will repeat for the third time as you keep missing the point. The F-35 was designed around the VTOL F-35B and an engine with 190kn of thrust. It was designed perfectly.
They now have an engine with 210+kn of thrust and lower fuel burn. The most optimised design is now different. The aircraft can be heavier while still maintaining the same thrust to weight.
Here is a perfect example. The F414 is the exact same size as the F404 but it gained 20% more thrust. What did Saab do with the Gripen E? They stretched it and added extra fuel. Are Saab engineers dumb? Did they get the fuselage length wrong with the original Gripen?
Nope. Someone somewhere in Saab is smart. Engineers at Saab worked out that stretching the fuselage was an obvious, low cost solution with no trade off. All thanks to the extra engine thrust.
The vast majority of development costs is the complex internal systems and sensors. A stretch of a F-35 fuselage would be incredibly simple. You wouldn't even believe that the section aft the cockpit and forward of the weapon bays is its own section that gets bolted together in assembly.
Now Lockheed could easily stretch this section. You can even see the leading edge extensions are part of this section. So the leading edge extensions can also be made longer which fixes any centre of gravity issues. A 1m stretch of this section would add more than 1,000kg of fuel capacity for less than 1,000kg of empty weight. The extra fuel would increase range considerably. Combined with the adaptive bypass engine the F-35C combat radius would be around 900nm. This is DOUBLE the combat radius of the Super Hornet.
With the improved thrust and mach angle the stretch would have no disadvantages over the current F-35C.
Just like how the F-16's are now flying around with 1,700kg conformal tanks and 50% greater fuel capacity and still have better performance than the original F-16A thanks to 30% higher engine thrust.