Great discussion!
A couple of points I would like to add (forgive me if they have already been mentioned). In aerial combat, the defender usually has an advantage in that it doesn't have to carry extra fuel to get to the target, it can be loaded with just a few missiles (and perhaps a gun) because he usually has a number advantage (many aircraft intercepting incoming aircraft), and a speed advantage (he can go faster for a shorter period of time because he doesn't have to conserve fuel for a long return trip). This is why the lessons from Viet Nam point to the fact that older generation aircraft which are often simpler and lighter can best a much more complex weapon system. But don't forget the US still had well over a 3:1 kill ratio at the begining (considered poor) and that by the end of the war, with training, new tactics, and weapons advancement, the kill ratio ended up at 11:1 during the final years. All that in a highly technical, heavy, poor dogfighting aircraft. If the rolls were reversed and Mig-17, -19, and -21s were loaded down with bombs intent on delivering them to South Viet Nam, lightly loaded (no fuel tanks, just missiles) F-4s would have had a field day because the roles were reversed and the Migs would be loaded for bear and had to watch their fuel if they wanted to return home and the Phantoms could use their speed and power to shred the attacking aircraft.
One more thing about the kill ratio in Viet Nam. The figures are misleading. The US aircraft that were being shot down (air-to-air) were mostly aircraft loaded with bombs trying to get to a target to take it out. Very few aircraft flying MigCap which were tasked to the air-to-air role ended down. So you also have to consider the mission profile the aircraft is loaded for. Just because an aircraft that is on a bombing mission has a few air-to-air missiles on board, doesn't make it an ideal air-to-air platform.
The reason for the difficult rules of engagement during the V.N. war were to protect against friendly fire when relying on BVR attacks. The AWACs of the day just weren't that advanced yet to keep track of who was who, and often didn't have the coverage of todays systems. That is why you see in the Gulf wars and other conflicts the West's aircraft using BVR attacks to shoot and kill hostile aircraft, you now can be (more) definate of who you are shooting at.
The argument for simpler light weight aircraft has been tried in the US before. After Viet Nam there was a cry that we needed a lightweight fighter (even though we had the F-5 which was a very good aircraft). Hence you had the flyoff between the YF-16 and the YF-17. The F-16 won the flyoff, but both aircraft ended up winning as the YF-17 later emerged as the F-18. But being the practical nation that we are, we demanded a lot more for our buck. So soon these very nice, light weight fighters, were recast in the mold of the F-4 Phantom II, by adding more and more equipment (and weight) to a nimble little fighter until they were no longer nimble or light. Now I am not arguing that it is a bad thing. We have two very capable aircraft in the F-16 and F-18, just that they aren't what they started out to be. I mean look at the F-16, it has lumps and bumps and humps until it is a long cry of that beautiful nimble and manuverable aircraft it started out to be.
The military philosophy seems to be that we need to do more with less, so aircraft have to be able to do everything, not just one thing well. I personally think that the F-4 Phantom spoiled military planners and they are constantly in search of that next aircraft that can do everything well.
