To me the single most important variable in A/C performance other than speed is fuel consumption and weight. Why? Because if a 10,000lbs A/C carry's 1,500lbs of fuel is fighting a 5,000lbs A/C with 500lbs of fuel he can compete only if relative fuel and ammo loads are equal for endurance. Otherwise he is forced to fight with an extra 1,000lbs of weight which ruins climb/accleration and turning ability. In real life this truth was proven by the success of the heavy fighter. In AH the light fighter rules because it is unaffected by the limitations of it's short endurance.
You certainly are obsessed with this "issue". Most wartime tests were conducted with full internal fuel. Most data you find reflects this. I would bet HT models the AH FM on such data. IMO all planes in AH should be forced to take off at normal TO weight. Use this as a minimum and work up from there. If some wants to fly around and burn off fuel then that’s up to them. With HT leaning to 512 x 512 maps make the fuel mod x1 and go through and match fuel consumption to the real data.
In AH the 152 always has fuel in its wing tanks, the a8 always has fuel in the 115-liter aft tank. The Soviets captured a "lightened a8" (W. -Nr. 580967) that weighed just 3986kg (normal take-off weight of 4360 kg).
If you are going open this can of worms I bet everyone who has a favorite plane can make a post describing instances where their favorite ride was "lightened".
Planes fought when they had to, whether like in Bodenplatte when US fighters had to up with full fuel to engage the incoming German attack or when low on fuel 262s were bounced when landing. You seem to argue that planes only fought after X amount of fuel has been burned off.
Heavy planes hold more E through a dive, they may accelerate slower but they will "zoom higher" and hold E as the pull out. In some instances there are advantages to "more weight". You may believe weight is the most important factor in your style of playing AH but I know many folks who fly with 100% every time in every plane they fly and don't think twice about it.
I would agree that with the density of planes and with the types of fighting in AH that in many instances being light has an advantage (I was/am a furballer) but that’s no more "real" then anything else in AH.
Here's a discussion they had over at AGW.
YMMV
http://agw.warbirdsiii.com/bbs/showthread.php?s=&threadid=26181&highlight=109g6