What is the advantage of making it take longer to get to fights when on the offensive? It seems to me that that could increase horde sizes as a compensation for the additional time it takes for reinforcements to reach the fight. Defensive fighters would still just fly at full MIL and WEP, as would the long ranged fighters and all bombers.
Larger horde sizes??? Because of a 1/8th less flight time???

Hordes are not because of anything other than some player's need for over-whelming force to get a base capture, that is it. Very rarely do we see the La's in a horde anyways because they don't have the staying time (unless fuel is managed) to hover over a base for the vulch.
My suggestion of a 2.5X burn rate would decrease current "flight time" capabilities by roughly 1/8th. Since most people are going to be concerned with the range of the La7 first and foremost, we'll use that as a test platform. Under the current 2.0X burn rate setting, at take off the La7 has 21 minutes of fuel at full power. Reduce that by 1/8th and we get close to 17 minutes, that is a reduction of 4-5 minutes. I hopped in to an La7 on the current LW arena map "Tagma" and upped from a sea level base and messed with the manifold settings just to see what I'd need to do to make up for the 1/8th loss of "flight time" capability. Here is what I found:
by reducing the manifold setting from 39lbs down to 34-35lbs at take off the La7 gained 4-5 mins of extra "flight time". With the slightly reduced throttle settings, the La7 climbed at 3000 ft a minute at 150+mph and once to 5000ft it was moving at 366 TAS before it hit the radar ring and it still managed to climb to 371 TAS just a few more miles further. For the La7 aficionado, they wont hardly notice that 1/8th less "flight time" if they can broaden their attention span beyond the trigger and gun sight. Case in point: The 1/8 less time of flight capability is not going to effect the length of time to the fight worthy enough to measure.
I'm guessing Spitfires are even less effected with throttle management, but I will test multiple Spitfires, 109's, and other aircraft with the 25-40min flight time just for kicks. I think the aircraft that might notice it more would be the aircraft that are already on the performance threshold such as the P40, but then again they have the larger fuel tanks to begin with so perhaps not. The only bomber that might be affected is the Boston III, it has just over 30 mins of burn time at max throttle under current settings, but then again it is a low altitude bomber not meant for those long range high alt bombing runs. The Boston III will adapt as well, I'm not concerned.
So again, there are three things that I propose with regards to adding importance to fuel: increase the burn rate to 2.5X; no DT available unless %100 fuel; and increase the penalty for the destruction of fuel tanks (2=no DT, 3=%75max, 4=%50max). Make fuel an important part of AH, not an after thought like it currently is.