+1 for a JA37.
Listening to the interview from Enigma - "Cold War Module Maker Interview: Magnitude 3" on YouTube, it's interesting to hear about the different sources of documentation, often from institutional archives, though sometimes from freedom of information applications (FoI). Not sure if a FoI application would be relevant to the JA37 flight documentation, and if that would lead to non-classified aspects of documentation being able to be obtained.
From a FoI application stand point I would assume it doesn't matter if it's "for a video game" or general interest etc, an application is an application.
A comment was made above about a " Cold War 1980s JA-37 with Skyflash " pre- more modern upgrades, perhaps there is more information readily available in the public domain for this. There's also the benefit that the Eurofighter is getting having people on the development team who flew and were instructors for the airplane for many years, ideally having someone to consult who actually flew a JA37 would be very useful for the flight mechanics,
Whatever the case, it would be great to see a fighter version of the Viggen for the Cold War server / era.