The subject title says it all. It would stop squadrons like Luftmorder (1Hunglo, Sally, Shobizzz) going into the MW and EW arenas and vulching each other to gain perks to blow in the LW arena.
By changing it so the perks you earn in an arena is only good in that arena would eliminate it. The only reason why these guys farm them is so they can up jets and tigers every sortie without actually having to work for them like the rest of us.
ack-ack