I'd like 4, but with a twist. I know this is too much to ask for but what the hell.
All enemy dots within a specified distance of an allied base, town, radar station would be displayed in flight. (simulates those stations radioing target information to fighter command.
When an allied plane encounters an enemy plane that is out of base/town/radar range, the target is painted, and is displayed on all allied radars until allied fighter is shot down, or contact with enemy is lost (Simulates pilot calling in enemy positions)
All enemy planes out of allied base range, and not encountered by allied plane, or flying below radar, not displayed at all.
(Fog of War)
Sorry for the long post, but a man can dream.