Great idea!!!! I wish try the campain.

It could be nice, but I do not know if feasible, take in consideration the increasing of pilot's experience during the campain.
This should be done measuring two factor: the number of enemy pilots shot down and the number of points collected (without take in consideration the points for the enemies shot down).
Of course every time you be shot down you will loose the pilot's experience and you have to start again.

Example: every 5 shot down or every 100 points collected you receive a bonus. The bonus could be:
+1 on the gun (at 1EXE/ 2EXE/ 3EXE) of distance;
the possibility to fire at 4EXE range (as was 3EXE);
the possibility to tail the enemy plane at 4EXE of range;
the pilots who have 100 points less than you, can not tail your plane;
you can do the restricted manouvres without any limitation;
you have a bonus to extinguish fire;
bonus to unjam the guns;
any other accetable idea....