You can add a lot of Type in an aircraft as long as they are not overlapping (contradicting each other),
Here's an example of F-18 java:
public class F_18S extends Scheme2
implements TypeSupersonic, TypeFighter, TypeBNZFighter, TypeFighterAceMaker, TypeGSuit, TypeFastJet, TypeNoOpenCanopyFly, TypeX4Carrier, TypeGuidedBombCarrier
public class F_18C extends F_18S
implements TypeGuidedMissileCarrier, TypeCountermeasure, TypeThreatDetector, TypeGSuit, TypeAcePlane, TypeFuelDump, TypeStormovikArmored
That's 14 types (excluding overlap) that is currently in the F-18. As for WWII aircraft, I don't think we'll need that much.
For what I mean, we would create a new type and add it to the aircraft java. In maneuver class, if the aircraft is an instance of that Type, it'll tell the AI to switch maneuver mode, drop what ever they're carrying and aggressively engage target or make evasive retreat. all the maneuver mode is already there, just need to make the link, the trigger condition, however, can be complicated. As long as it satisfy the condition, it will trigger the effect, there's no priority, AFAIK.