So let me get my head around this, the production aircraft has not flown, it has yet to be certified into the far inferior FAA Experimntal Category, they are potentially lead customer and they are to assume service delivery, should they win the competition, from 1 January 2020? Good luck!
Air-to-Air: Assuming this is training in support of Typhoon and Lightning with some form of Electronic Attack, Radar and DASS to enable representative adversary replication all the way to the merge then I'm not convinced, aerodynamically, that it will be up to the job. I'd probably include RAF ABM and RN FC training in here as well.
Air-to-Surface: Assuming this is the maritime domain then it's significantly less representative than a Hawk for a Red Air fast jet threat or simulated anti-ship or anti-radiation missile and no real improvement than a business jet for any electronic attack work in terms of performance.
Also, can somebody please tell me exactly what MOD contract HHA currently support with aircraft that are 50 years old? I did chuckle at the Air Clues article and am surprised the RAF Flight Safety team entertained them.