Well, I can see this thread has digressed into a gameplay issue. Wobble, Soda, Lepton, Wardog, MiG Eater you are ALL making good points. However, I feel the gameplay needs more balance regarding fuel tanks.
Wobble is correct, by reducing the fuel to 25% you do NOT deter point defense of that field. One can still take off and get to 10k to shoot down incoming bombers or kill cons. Period. That is a FACT. With that fact established, there's not a whole lot of point then to take fuel bunkers out as most fighters get vulched or some such thing. Also, Soda et. al. you also make a good point in that if one only takes the fuel down there's NO POINT in going after the FHs. That would make it TOO easy to capture a field. Now, let's look at the reality of the game. ALL countries have a hard enough time as it IS to even organize a single coordinated strike against one field let alone fly to all the surrounding fields and knock down their fuel to 25%!!! (gee that sounds like fun don't it). So, in AH reality that strategy (IMHO) is worthless in its execution (don't get me wrong - strategically it's very sound but in reality it just won't happen).
So... how does one balance it out fairly and make the fuel a worthy target (which by the way Strategic Daylight Bombing in WWII definitely went after refineries because of its importance and we do have refineries in the game). I like Wobble's suggestion to limit only 5 (or some other number of vehicles) fighters to take off after fuel has hit zero (0). Zero fuel would then prohibit anything from taking off for a SHORT period of time (i.e. 2,3, or 5 minutes or whatever) at which point it would bump back up to 25%. This would add some real importance to the fuel. Heck make them harder to take down but it adds another strategic element to the game. Right now, it's only a nusciance to be at 25% fuel while defending a field. I will only blow them up for the fun of it and to get perk points on my missions. Tactically, I see them of little importance.