As it is, there is no strategy in the fuel aspect, or rather there is very little. Fuel is an afterthought in most cases, and in many cases not thought of at all.
Reducing fuel to 50% max with X number of fuel tanks destroyed will make people think twice about taking up an La7 or other such easy mode plane. The Spitfires, in general, will be just fine.
The only few fighters that would truly be retarded would be the La5/7, I-16, Yak-3, and maybe a few others. The only bomber really affected would be the Boston III's. But then again, we're talking about a few runs with field supplies in an M3 or C47 and *puuf* up goes the fuel tanks. It would impact the game far less than ordnance bunkers and barracks, because EVERYTHING is still available just not for the length of flight normally taken. Besides, just how many of the gamers take an La7 with 100% anyways?
Fuel tanks and barracks both could use a tweak. Ordnance bunkers too for that matter. Having a tiered system would do more for game play, imo. I think the "all or none" approach to the HQ, ordnance bunkers, and barracks is more restrictive on game play vs having a tiered system.