There have been some good threads recently on AH flight models and the performance of existing rides (see Widewings "thoughts on the current flight model" and mws "mustang performance" threads) that have brought up some interesting points. Some unanswered questions remain though:
1. What, if any, changes should be made to existing rides?
2. What effect will it have on gameplay?
I've got a couple of ideas, so I'll throw them out for general consumption.
First, its clear from some of the data in the other threads that the performance of aircraft of a given type varies. The May 1944 P51-D running on 130 octane fuel at 67" of boost does not have the same performance as the March 1945 P51-D running on 150 octane fuel at 75" boost. There are many other rides where this is also the case - Spitfires, P47s, some P38s, Me109s, etc.
Now I can see why HT wouldn't want to unbalance things by, for example, making all P51-Ds the March '45 model, as it leads to the continual overmodeled / undermodeled debate that gets us nowhere, and probably screws up gameplay by suddenly having 60% of the sorties being done by late-model P51-Ds. But I think there is a way for us to have our cake and eat it too: how about introducing multiple variants of the same ride, and have the higher end models have a perk cost?
For Example:
P51D - 8th AF May, 1944 Eny: 8.0 Perk Cost: 0 (67" Boost)
P51D - 8th AF Dec, 1944 Eny: 6.0 Perk Cost: 5 (72" Boost)
P51D - 9th AF Mar, 1945 Eny: 5.0 Perk Cost: 10 (75" Boost)
Variations of this can be done to Spitfires, 109s, P47s, etc.
What this does is model the variations in each type over its operational life, and in effect, adds new rides to the game with a minimum of work to HTC since we are taking existing rides and making minor modifications (adding engine power) instead of modeling entirely new rides.
Variations on this theme would also allow for optional perked weapons loadouts:
For example:
109K4 - Dec '44 Eny: 20.0 Perk Cost: 0 1 x 30mm, 2 x 13mm MG, 1.80 ata boost.
109K4 - Dec '44 Eny: 15.0 Perk Cost: 5 1 x 30mm, 2 x 20mm gondolas, 2 x 13mm MG, 1.80 ata boost.
-or-
109K4 - Mar '45 Eny: 10.0 Perk Cost: 10 1 x 30mm, 2 x 20mm gondolas, 2 x 13mm MG, 1.98 ata boost. (hey, I can wish for it

)
From the gameplay perspective, adding perked variants to existing rides gives everybody new rides to try out. Having the high-end variants have a perk cost limits their usage, gives us something else to spend perks on, and provides an incentive to bring the rides home (although the cost isn't too severe if you just want to auger).
This also works in all arenas easily - you can do a perked variant of the Spit V or the Mossie in MW with the higher boost, or make the 109G2 gondolas a perked option.
This can be combined with the ENY limits as well - for example:
if we have this setup
La-7 - Feb '45 Eny: 5.0 Perk Cost: 0 2 x 20mm cannon
La-7 - Mar '45 Eny: 3.0 Perk Cost: 0 3 x 20mm cannon
then La-7s are still available when the ENY hits 4.0, but you just don't get the 3 cannon option if you are on the side with the horde.
The variation in rides also adds a bit of uncertainty to the game - if I'm in a 51, and get jumped by a 51, I can't be certain if it is a May '44 model I can run away from, or a Mar ' 45 model that can crank up the boost to 75" and run me down. Neither one of us can be sure what the other guy has "under the hood", so it adds another dimension to the fight.
Think on it a bit HT. A system like this gives us more historically accurate modeling, and better overall gameplay as well. It gives us an entirely new set of matchups to our furballs (Mar '45 51D / 75" vs Spit XIV / 25lbs, etc. etc. etc.), as well as providing something new and interesting to fly without having to spend a ton of time modeling.
EagleDNY
$.02