Just an idea...
I would like more options to mark fuel settings other than actual 25, 50,75 and 100% too.
But I have a distinct point of view about fuel quantities.
In the real life we don't measure fuel with percentage; only in liters or gallons.

Let's presume a partially damaged field with only 50% of fuel... With actual fuel model, I can take-off a P-51 and do my attack or defence flight mission for long time because P-51 have huge fuel tanks. The BF-109 would be my last choice because high fuel consume... but 109's have small fuel tanks too !!!
50% of fuel in P-51's tanks represent more gallons than 100% fuel in 109's tanks, I think !!!
The actual fuel concept isn't fair or reasonable in my mind !!!
The great AH differentiation over others online "sims" is the better game concept. For the guys with this responsability on hands... think about!