I like the sound of the F/A50, but its already run into export problems because of the inclusion of the F404 engine.... What does it cost, comparitive to the competition? That might be a key aspect too.
When dust clears, I still think it's the F-16. I don't know the specs of trainers but for the role specified, it seems to be even a "lesser" Viper would be better. Arms re-exporting restrictions may altered a bit soon. I can't see western defense industries giving up marketshare in a widening market, especially with Russian products being relegated to the dollar bin (when available).
With so many political, diplomatic, financial and intelligence/technical barriers to F16 export, I'm wondering if there needs to be an alternative: something that can take on the most numerous fighter opposition its likely to encounter (Mig29/35, Sukhoi27) - but not at the purchase, operational or political cost of an F16?
A Su-35 is a worthy opponent, and who knows where the subsystems come from, and with what strings attached? It will take money, $20-30 mil USD per unit minimum, I'm guessing.
Operational cost could be lowered with good design aforethought -- designing around maintenance, reusing layaround avionics/chipsets/engines/other parts to ensure cheaper build and repair stocks, that sort of thing.
Political cost is probably going to face the same hurdles as we're seeing now, both because of political involvement itself, and also tech-transfer issues, so that's hard to say.
The US went the lightweight single engine route with the F-16. Conversely the USSR had this already with the MiG-21, but abandoned this route for the heavier twin-engined fighters, pursuing more the F-15 than the F-16.
Why did the Russians entirely abandon the single engine agile fighter after the MiG-21. Of course the twin engine MiG-29 is no slouch, but at twice the cost. Perhaps the Russians did not have an engine capable of giving the reliability and power needed to create a Soviet F-16.