Using the Black-Red-Gold in a game is not an issue, as long as it is used for either the federal republic of germany or the weimar republic, both of wich use this flag (or used, in case of the weimar republic...). And i don't think that the Black-Red-Gold would trigger anyone, if used for those states. Sure, the weimar republic had its problems, but those were mainly internal politics. The issue is that it is used as the flag of the 3rd Reich, wich never used it. My biggest issue is that we as germany have come a long long way since the 3rd reich, and using our flag as the flag of the 3rd reich is just wrong.
I mean, a US-citizen would probably also be outraged if the confederate flag was used to represent the US in 1940.
Yes, using the Black-White-Red flag would be much better, because that was the flag of the 3rd Reich from 1933 to 1935, after wich they switched to the Reichsflagge.
The reason why i think this may get the game banned in germany is ยง90 StGB, wich states that denigration of the state and its symbols (including the flag), is punishable with prison. And using the current flag as the flag of the 3rd Reich may be count as denigration. But i am not a lawyer, so not quite sure on this.
Edit: Just saw that they changed the Flag to the Black-White-Red with an Iron cross, so it's fine now!