Bombers in WWII did not take off w/o %100 fuel in WWII. There were too many things that could go wrong while navigating so going 2-3 hours off course was not uncommon.
I'd be willing to bet the same thing was true of fighters.
I also believe that there is already enough "stacking the deck" BS, otherwise known as "gaming the game" already going on.
I'd like to see no DT unless you have %100. And no less than %75 fuel. The %25 option is 
I can see much more of an argument for less fuel in fighters. I'm not sure I agree with 25%, but in some extreme cases where planes have massive amounts of fuel storage (P-51, P-47N, Mossie) I can understand it.
Fighters did take off less than full sometimes. However they act much more like the real thing in here than bombers do. I'm of the idea that we need different rules for heavy bombers vs fighters. The current system benefits bombers far too much. We need an 8x fuel burn for buffs. Separate fuel burn leaves fighters as-is, but will force bombers to take 100%. You still get the compressed time due to fuel burn, but the climbout phase will be slower (heavier weight) and the handling worse (more historically accurate) or will force most people to cruise at max cruise settings... Something they never do now.
So, fly light, but fly slow and lower, or fly full gas, with worse performance but the ability to run full throttle more. Either way a balance is struck bringing the level bombers back down to a level befitting WW2 bombers.
They are already very well defended, if you look at the .50cal armed planes. It won't stop them. It will simply encourage them to fly slower or lower. Whatever the choice made, the end result is slightly more historic.
