I'm kind of suggesting the opposite of what the F-35 project did - which is, to my understanding, was to sell the same plane, with slight variations to the thre

I'm kind of suggesting the opposite of what the F-35 project did - which is, to my understanding, was to sell the same plane, with slight variations to the three branches, all of who have wildly varying requirements. They tried to maximize commonality between the 3 variations, but from what I can tell, this plan hasn't worked out, and they've ended up building 3 different planes that happen to look similar. My suggestion was to drop the pretense of building the same plane for the French and the Germans - but use the same (or similar) engine for all planes, use the same or similar radar, and avionics, and put them in different airframes. Afaik at this point, one only needs to reprogram the avionics with control laws for each specific airframe. Then let each nation put their own sensors and bits and bobs to satisfy their own requirements. From what I've read, the Chinese are sharing the engine, radar and avionics tech between the J-10 and J-20 fighters.