Yes, there were spies in WW2, and what was done to them if they were caught?
I think friendly fire should be turned off for such a player for one month, and their dot should always appear on dar for a month, no matter the radar range or alt.
Maybe with a special yellow colour.
So all can see him, and all can shoot him with impunity.
Hell, give him a 10 mile icon too, with range always on, even in a GV.
its great that someone wants to play historically and be a spy. But there is a price if you are caught.
If they do it and never tell anyone, or do it and keep it tight between them and other like minded idiots, well and good.