Put it another way: In a fight, you win not by fighting under your opponent's rules but by forcing him to fight under yours. And cheating is allowed.
If you have less soldiers than your enemy but your soldiers have longer distance rifles and are better marksmen, they why would you want to go into combat within your opponent's reach? You would not. Your opponent have more troops, that is a 'rule' that you do not have. You have longer distance rifles and better marksmen, two 'rules' in your favor that your opponent does not have. So why would you want to get into a shooting match within his inferior rifles' distance, especially when you have less troops than he?
But the major problem for your advice, while in theory is true and admirable, in practice it is extremely difficult to apply. Assume that the Su does have a higher IR signature. The question then is how are you going to apply the 'exploitation of weaknesses' advice in training, in other words, how can you simulate that higher IR signature in as many variety of combat and flight situations as possible for your pilots to learn how to spot and exploit?
Infrared, just like radar, can vary according to target aspect angle, meaning how the target is facing (viewing) you -- the seeker. Not every aircraft is going to produce the same intensity and the more maneuverable ones can deny you that information really quick. What can you do to replicate those conditions to confuse your pilots in training so that they will not be confused in a war?
This is a real problem and it is real enough for US that we ended up with Red Flag and these guys...
4477th Test and Evaluation Squadron - Wikipedia, the free encyclopedia
This forum have a former F-15 pilot. Odds are good that he faced a MIG-21 in training. The US have nothing in inventory that could match the -21 in air combat maneuvers, as in how quickly can it turn, does it have any unique in-flight behaviors that could help our pilots in predicting what a -21 pilot must do, how can a -21 pilot exploit his small size, what altitude is the -21 best at, all these advantages are 'rules' that a -21 pilot can force his opponent to fight under. Then the -21 pilot win.
Can you train a soldier to be a sniper so the rest of your army can learn how to deal with snipers? Yes. But can you produce an Su so your non-Su pilots can learn how to deal with an Su should that day ever come? If not, then what do you have that can come close enough?
For US, we had to get real MIGs. Then it was decades of learning and simulating and learning how to simulate that we now can comfortably part with our MIGs. But even so, every US military service have a 'Foreign Technology Exploitation' office whose work are top secret.
We do not want to go to war but unless we actually literally kill ourselves in live fire war games to have real combat experience, we should have training programs and regiments that should come as close to real as possible. In my days and that was during the Cold War, we have inspectors walking around putting red tags on people to indicate casualties and deny the unit manpower. Today we have laser tags to virtually 'kill' a soldier. At Red Flag, the only limitations are altitude and live missiles.
The point is this: War and combat are confusing enough so the goal should be to have as realistic of war and combat training as possible in peacetime so our forces can have as many combat instincts as possible to increase their odds of survival in a real war. That is why we have Red Flag and Fighter Weapons School. That is why we conduct revealing and embarrassing exercises like the Millennium Challenge that so many misunderstood to be the end of the US Navy in a Persian Gulf scenario. These gullibles are so wrong and they do not even know it. That is why Desert Storm was so shocking to most but not to training specialists worldwide who know of our training programs.
If:
In a fight, you win not by fighting under your opponent's rules but by forcing him to fight under yours.
Then:
In peacetime training, you should have as many of your opponent's rules as possible, or as close to real as possible, so your forces can study and learn how to avoid getting trapped by a real enemy.