In a sane world, ground forces would professionalise the JTAC role to reduce the initial training burden and focus an expensive resource on recurrent training. Indeed, maybe the RAF Regiment could have filled this role in the same way USAF Air Support Operations Groups do for the US Army, instead of basing its existence solely on the argument that ingrained "air awareness" is needed to defend airbases.
In an even saner world, JTAC training would be carried out exclusively using simulators, with non-representative types such as DA42 used if real-world confirmation is felt necessary. [How is a BDU-33 drop "representative" training, anyway?] Contracting civilian-operated FJs on such tasking in today's cost-, safety- and environmentally-conscious world isn't justifiable IMHO.
I recognise that the worlds of inter-service politics and NATO standards are not always sane ones
