UK & EU already developed/deployed/use in warfare those and building next gen{Hi} version & we still trying to build a complect jet with those.
There is a huge difference and again there is difference b/w Hi tech vs Lo tech and both share same things you mentioned.
Collaboration between two or more countries when one or both of the conditions are true
- Their is a financial limitation when either of the countries can't/won't independently develop, manufacture and use a technology
- Their is a technological limitation when either of the countries can't/won't independently develop, manufacture and use a technology
In our case first case is not true as we can bankroll our R&D by ourselves.
Second condition is true of us when we talk about engine, rest we are confident we can do by ourselves.
In case we want to get a technological we always go to Israel. Their technology is second to none and comes with no strings attached.
If Israel has turbofan technology we would have collaborated with them as in case of Barak-8.
In Barak-8 we didn't have seeker technology which we got from Israel reset was done by us.