Perks/Sortie would not necessarily, and truly, reflect what you are driving at.
The "perk multiplier" is constantly being adjusted by the "numbers/ENY" in each country.
You could be forced to fly only real high ENY planes (example: Spit I) and still have a perk multiplier of 0.0something, while at the same time, a guy could fly a N1K on the low number team and be working with a perk multiplier of 5.
If the perk multiplier was static, then this might work.