Not much of an amateur - expert as you, but from whatever I've read about aviation out here & elsewhere, do tell of the first instance where a newly concieved & developed engine would have been mated with a newly conceived and developed AC. And I'm not referring to the dawn of aviation.Why? The regular Kaveri is already ready for integration with Tejas. The same engine, albeit modified, will be used to power the IUSAV.
If not, why should Tejas be the first. Then again, if ADA / DRDO / GTRE are full of optimists, hell, why not?