Well it may be worth exploring the question from their POV, but I think they would find the answer is no. There are almost no potential buyers of such a Jet other than the partners mentioned. They couldn’t sell them to Arabs, and they couldn’t sell them for NATO deployment, so it leaves them in a consortium that would compete with the F-35 only in theoretical (and perhaps one day real) combat.
I mean if Russia, India, France, Israel and maybe Brazil build a competitive plane, they would be the only ones to fly it, and if there was a hot war involving these countries their plane would go up against the F-35.
Though you might wonder what capabilities Israel really needs. I got the sense they were buying the F-35 because of political pressure. AFAIK they would prefer and still want the F-22 which was never made available to them.
Do they really need the new fighter jets? Or would their money be better spent on anti-aircraft and anti-missile technology, and UAV bombers?
The only reason they would need F-35 is because Saudi Arabia will want some. US will give Israel money to give to the JSF developers because the Saudis will be paying cash for them. It’s a very strange set of circumstances.
Put it this way-if say one of the following-Russia/India/France/South Korea/Brazil partner with the Israelis there would be a minimum market of at least 400-500 aircraft between the two partner nations, which could stretch to a few hundred more by exports to stable customers. That’s not really a bad count by most yardsticks.
The fact is that all the nations mentioned have some or other 5th generation fighter plans at various stage of conceptualisation or development. And there’s increasing cooperation as well-India is tying with Russia while the South Koreans recently inked a contract with Indonesia (with Turkey also interested) to devleop new fighters.