As you said, the incentive would only be for people who care about rank. Is that the group who's behavior needs to change?
It is a group where change could be induced without too many side effects. Because everyone can freely choose if the effects apply or not. It doesn't sound like adding an incentive to fly higher-eny planes for score-lovers would actually hurt anyone. Neither anyone ignoring score, nor anyone flying for score (because everyone flying for score has to fulfill the same rules, and as such the playing field is kept level).
There is a group of pilots who BnZ in fast late war planes.
There is a group of pilots who care about score.
What's the overlap? Is it sufficient that incentives for the second group change the behavior of the first group?
There's some overlap, but both have a very low overlap with the large group that actually plays the team objective, and neither flies fast BnZ planes nor cares too much for score.
Would I prefer my opponent to play the objective, too, or would I prefer my opponent to just BnZ? Obviously, the latter. An opponent that works on a different goal is much less of a problem than one who actively works against my goal. But then an opponent that just plays for score (or a sub-part thereof, or landed kills, or similar) has a choice of tools that can be a lot more fine-tuned for the a2a engagement than any choice to play the team objective could ever be.
The objective and the way the game are played are two separate things. Whatever the objective may be, the way it is played is by some kind of fight (excluding resupply, but that's another topic). And those fights come with an imbalance between players playing the team objective and players playing the score objective.
And thus it would make a lot of sense to add some incentive to score to fly lesser planes, just like playing the team objective basically requires specific plane choices for the intended purpose.
To make that really work, the value used for score should be pure a2a capability. ENY today also depends on the ability to carry ordnance. Probably not because its much more an achievement to shoot down a plane that can carry bombs to earn more perk points, but maybe to make sense for the ENY limiter / side balancer (which didn't exist when the ENY values were invented; I think ordnance-carrying ability has always led to lower values).
