Let's suppose a mission with perk planes. I suggest that the mission builder have the option to donate perks if the putative pilot has less than 2x (aircraft) perk points.
For example, I currently have approx 130 bomber perks. If I join a 'Battle of the Bulge' bomber mission, I would not be eligible to receive perks. However, I have less than 100 fighter perks, so if someone were to post a mission with just about any perk fighter, I would be eligible.
This would enable those with vast amounts of perkies to put their Perk Points to good use.
As for the rewards, I'll open the floor.