This is not a very sound argument. By this logic, GE404 should have been phased out as soon as 414 was developed and so on.
The reality is that, there are always different engine and thrust requirements based on different classes of fighters from light combat to air superiority fighters.
With regards to using a detuned AMCA engine for Tejas for midlife refit, again several holes in this logic.
- The initial consideration for Tejas MK2 was a MK1 airframe with GE414 engine to provide additional thrust and payload. This was soon realized as not very viable without airframe changes, hence the current MK2 design.
- Now imagine what it's going to take to detune a 130KN engine down to 85-90Kn. At the very least you are to be struck with extra weight which will be detrimental for SFC/Range.
- Even if it were feasible, that's 12-15 years out assuming that the base AMCA engine is developed in 10 years which in itself is questionable with a brand new project. Neither Safran nor Rolls have a 5th Gen engine of this class. So this is an ambitious project for them let alone GTRE.
- GTRE already has a functional engine with 73KN thrust demonstrated per public records at least 5 years ago. Whose to say they have not made progress since then to increase thrust and reduce weight while resolving flutter in the AB section. I would be surprised if they have not already. I would be surprised if they have not made some progress towards this in last 5 years but have not made it public.
- Development of an 85-90KN engine will benefit Tejas, HLFT42 and potentially even TEDBF depending on when it gets CCS approval.
In summary, Kaveri 2.0 can be closer to fruition than AMCA engine if the government pulls its finger out and provides adequate resource on this project.