but for me I would favor the T-50A with an upgraded engine probably the F414
How about the clean sheet designs? Are they out of the question? And BTW, one of the "clean sheet designs" is from SAAB who has a mature small(ish) fighter equipped with the F414. I'm confident it could be the basis of a very nifty high performance trainer. And it already has an EASA radar, so if USAF wants a real radar and not a simulated one in some of their trainers, SAAB already has the ability to provide it. And the F414 already has a very well laid out growth path in the Super Hornet, with Boeing offering a version with something like 20% more thrust. So SAAB may be on to something.