The whole problem, the way I see it, is that in the MA you see 6 spits for every 1 type of other AC in the air. You see 3 or 4 La7's for every 1 other plane type.. and 2 or 3 n1ks per every other plane type.
Now, LW iron and P-51 make up *most* of the "other plane type" seen in the air, P-47s, italian rides and zero/ki-61 are rare.. P-38 was rare up until last tour (and even then most 38s you see are kamikaze planes).
And that in essence has grown so old and so annoying that it would be nice if something was done to change it. Now Mandoble/Tumor/etc suggest light perk cost or RPS or what have it. Others just say shutzefukup, and a few just like to lurk around and start flamewars or make themselves look good by bashing other's points of view and opinions. *shrug*
If it was up to me i'd perk every plane above its earliest model. For example:
Spit 1 : free
Seafire : free
SpitV: 1 perk
SpitIX : 2 perks
Spit 14: 20 perks
109's
109E:Free
109F:1 perk
109G2:1.5 perks
109G6:2 perks
109G10:2.5 perks
P-51B: Free
P-51D: 2 perks
P-38F: Free

P-38J : 1 perk

P-38L : 1.5 perks

P-47D11:free
D25: 1 perks
D30: 1.5 perks
190A5:free
F8: .5 perks
A8:1 perk
D9 : 1.5 perks
152: 20 perks
La5:Free
La7: 1.8 perks
and so on.
The way I see it, a light perk cost like this would create a "market" for the perks and have them be used constantly. The perk cost would make the late war planes be expensive to up constantly IN the long run (since late war killing early war=very little perk gain). It'd make the MA more varied in A/C. Of course, the eny/obj would have to be modified a bit so that an La7 would need to kill a few (say, 5?) spit 1's before he can "repay" his La7 perk cost.
Just look at the CHOG. I mean, WOW, when they were unperked the only thing you'd see was F4U all over the damn sky. It got real old real fast..plus the added aggravation of its ungodly guns/ammo load. It was perked at a relatively high 8 perks to start with.. its usage DROPPED like a brick. But I think it wouldve still dropped dramatically if it had only costed 4 or 2 perks to up. The same effect can and should be applied to all planes in the MA, it'd keep things varied (or at least more varied than now).