I saw somewhere someone wanted to provide a motivation for people to fly "safer" to maintain longer streaks. In other words to punish those who do a strike then auger to bring in the goon etc. Here is an idea to accomplish that. Make your Perk Points within a streak not simply cumulative but multiplicative. Say you get 3 perks for a shoot down, then you make another shoot down worth 3, instead of getting 6 total perk points, you get 9, 3 times 3. Hmm this wont work with fractions though. Well, you could add some kind of formula to do this effect. Say the first Point source is normal, the second is doubled, the third tripled, or quadrupled if you wanted to make it truly exponential. Etc. This would have to be carefullly worked, so that people wouldnt just go off with 20 100lbrs to nail gun emplacements all day. But there is room here to truly motivate people to keep from being shot down or captured.
