Would also need a bigger wing, fly-by-wire to meet the manouverabilty requirement.
You really that into nostalgia?
You don’t understand the issue.
It is not an upgrade - it would be a new-from-the-factory airframe.
It does not need to be fly-by-wire and does not need the maneuverability of a fighter - it’s a trainer. It teaches pilots how to fly, not how to dogfight, an advanced skill set. It focuses on essential skills to be an aviator, instruments, formation, acrobatics, high AOA handling and swept-wing approach and landings.
It is not an F-20. It needs to be a two seat aircraft to accommodate an instructor.
It does not require a full weapons suite. The only reason a limited weapons capability is required in the new trainer is that the F-22 and F-35s are too few and too expensive to accommodate all the weapons system initial skills training that was part of all fighter syllabus in the past (F-4, F-16, F-105, F-15). So they want to offload it on the end of the pilot training program.
Nostalgia? That’s what the Air Force did when it replaced the jet T-37 with a prop trainer.