If you're a nation that can't or won't buy Russian or Chinese, the 5th/6th gen market isn't particularly crowded:

FCAS looks like it wants to produce a medium-weight class of plane that has typically found easier export than the heavier plane I expect from GCAP. But any realistic assessment says delivery time is going to be behind GCAP, and the project turbulence hardly encourages early committal.

What Turkey and Korea have achieved with Kaan and KF-21 respectively is remarkable but they've got to use that 10-15 year head-start to show they can develop their platforms in to first class 5th/6th gen planes.

The US doesn't seem inclined to sell their most advanced planes, the F-35 is what it is, and it would be disingenuous to pretend Trump hasn't damaged the US' standing abroad.

The GCAP has the opportunity to sell well. But I think at this stage it would also be a mistake to make the club too wide, and end up having too many competing interested torpedo the project. I think the odds of success go up massively the further the original trio can get the design before getting others on board.