Is rewarding one behavior penalizing another one? Think about it just a little more karnak... I know you can do it.
No. If it were I could consider Bill Gates to be penalizing me because he makes more money.
You aren't enticing people to fly other planes by giving them extra perk points... you're effectively reducing the number of points for what they are currently flying.
Not by all that much though given than a large percentage of their kills are made up of Spit IXs, N1K2s and P-51Ds. Aircraft that they now get only a perk point for and for which they would still get a single perk point. They'd actually get a little more for the La-7 than they do now.
Yes, they would get less for the rarer aircraft, but they hardly get anything now so it isn't much of a real number reduction.
Keep in mind that the current system does this same thing, just not to the extremes of Urchin's idea.
Above and beyond that players who are on the edge of flying other things besides the Big Four would have a reason to do so.
That way... the people the fly the off-beat planes can afford even... um... more uber than the otherguy's planes?
That is the idea of the current perk system too. Urchin's idea hasn't changed that at all.
To change that it would have to be set so that getting a kill in the Spitfire Mk IX (first place killer) would get you just as many perk points as getting a kill in the P-40B (last place killer). Does that sound like a good idea?