We're back to "make the fuel harder to kill" again.
That's the only real change your improvement would make, since there is ABSOLUTELY no difference in the amount of fuel available to each plane under your "improved" system. It's simple math. Here's an example.
Assumption: P51 holds 500 gallons, spit holds 100 gallons (both incorrect, but useful for example)
Fuel at base is 75% of 10000 gallons max, or 7500 gallons
Fuel can be porked to 0%
Current Method:
P51 can take .75 x 500, or 375 gallons.
Spit can take .75 X 100, or 75 gallons.
Fuel left after both up is 75% of infinity, or infinity.
Your Method:
P51 can take .75 X 500, or 375 gallons.
P51 can take .75 X 100, or 75 gallons.
Fuel left at base after both up is 7050 gallons.
My Method:
P51 can take 500 gallons.
Spit can take 100 gallons.
Fuel left at base after both up is 6900 gallons.
The effect of your system is to keep the fuel penalty in place for all pilots, and eventually reduce the field fuel supply to zero. This will piss off the furballers, since they are penalized both ways. The strat guys won't mind, however, except maybe the vulching wouldn't be as good.
The effect of my system is to allow all pilots to use whatever fuel load they think is appropriate, up to the limit of fuel available on the field. That will make the furballers happy, since they can use enough fuel to get to the furball, and won't affect the strat guys too much, since the base can be porked for capture.