Stiglr,
I thought you were the guy so keen on realism?
Your suggestions fail, on both counts, to encourage, as accurately as possible, WWII air combat tactics. "Both Die" fails because it encourages gamey behavior, namely ramming when rams cannot be dodged, and encourages people to stay at longer ranges that should be required. We're not talking about a few feet of lag induced displacement like in a FPS, we're talking distances in excess of 100 yards at times, depending on total ping times and on the speeds involved. By no means would head ons be the only things affected.
The second suggestion, only enforce a collision if both players see it would pretty much remove collisions from the game and encourage people to fly through their targets, guns blazing. That is a severe distortion of combat tactics.
These games already have enough factors, such as no fear of dying, distorting tactics, more things doing so won't make them better.