Everyone appears to accept that without effective low-observable characteristics the core aircraft would not be a particularly capable platform.
Everyone? I've read quite a few accounts about the F-35's wonder electronics providing an entirely new capability and synergistically providing increased capability/lethality to legacy platforms. And many of those accounts are from USN, which is MUCH less committed to the F-35 than USAF. It will be interesting to see if the F-35's electronic capabilities can be successfully transferred to legacy platforms. I would think yes, but I don't know enough about the details of those capabilities nor how they were achieved to be sure. In other words, there appears to be more to a 5th gen aircraft structure than just stealth, with many sensors and systems apparently needing to be integrated into the airframe and not just scabbed on.
And regarding the F-16 Block 60+/F-16V which is currently available to many Air Forces, many of those Air Forces are choosing the F-35 instead. I'm reasonably confident there is a very good reason for that, and that reason is
not the oft repeated claim that LM lies thru its teeth and the various national procurement authorities are just too naive to see it.
It [F-35] does not accelerate particularly well, shoots its missiles from a much shorter range, has relatively poor agility, bleeds energy rather quickly and (when utilising its USP) does not carry much.
These are interesting performance claims. Based on what and compared to what?