Couldn't AMCA be the demonstrator of the SCAF NGF? It could receive constructive criticism from Dassault who know how to make airframes lighter while improving their aerodynamics and strength. The final NGF would probably have a new variable cycle engine and more advanced on-board systems with new capabilities.
Any SCAF demonstration on AMCA will have to be a parallel project.
Unofficially AMCA already has entered the engineering phase, procurement of long lead items began last year.

Midhani supplies titanium alloy for medium combat jets’ airframe | Hyderabad News - Times of India
As India works to further strengthen its armed forces by equipping them with the advanced medium combat aircraft (AMCA), Hyderabad-based defence PSU,

France should have offered it as part of Rafale offsets a few years ago.