Discouraging the unrealistic "Joust"
Combats in WWII did not involve the use of Immelmans immediately after head-on attacks. Yet this is what tends to happen in WGS.
There was a reason for that: in the time it took a plane to do a horizontal turn of 180 degrees, an aircraft could just about do a split-S or half loop upwards, but in a turning fight, shooting was possible, while in a split S or Immelman, it wasn't. Furthermore, an aircraft going vertically upwards and then rolling horizontal was an easy target.
Suggestion:
Firing is forbidden during both the straight before an Immelman, the Immelman itself, and the straight afterwards. In the Immelman any firing at the aircraft gets an additional A chit.
The effect of this is that after a close in a head-on pass involving a straight the aircraft cannot immediately immelman on the enemy's tail and start firing. It must do yet another straight, then an Immelman, then another straight, before it can fire again, having completed a 180 degree vertical turn. Meanwhile, the enemy has the opportunity to also turn 180 degrees (horizontally) in the same 3 cards (for most aircraft).