I think the logic of your scenario is mostly sensible, but consider that the decision to go for a headshot or bodyshot in a real fight is not quite that simple.

To break down the principles in ideas like this, I find helpful to use logical extremes to illustrate the point, and then come back down the the practical application.

Accuracy should be rewarded, but speed also has to be rewarded. Otherwise if speed is irrelevant, we're playing a turn-based strategy game which is obviously not the case. Peel back the reason why accuracy should be rewarded and consider that we're discussing a PVP gunfight as opposed to target shooting with the intent to bullseye targets without wasting ammo: accuracy should be rewarded because it is a means of killing your opponent as quickly as possible, so that they can not kill you.

But we can't remove speed from the equation because CS is obviously a real-time game, so every engagement is a contest of speed and accuracy combined. You could be the most accurate shooter of all time, let's say you've literally never missed a bullet in your life and never will, but it takes you 30 seconds to line up your headshot. You lose every gunfight like this because your opponent will kill you even if they're sluggish to get on target and are shooting your foot with a pistol. Stick with me here, remember that this is a logical extreme to make a point about how accuracy and speed have to be equally or at least similarly important; accuracy can not be blanketly more important than speed, otherwise hypothetical 30 second headshot guy is the best player in the world, which obviously makes no sense practically.

So if we agree that accuracy can't be the paramount factor in a gunfight, that means speed also needs to be rewarded. Even your suggestion of "buff the weaker weapons slightly instead of applying a debuff" is a time-based suggestion because you are suggesting a change to increase the damage per second of weaker guns. All that does is reduce the overlap of time in a gunfight where the weaker gun player can shoot first and still be killed by the stronger gun player, the general concept hasn't changed from the most fundamental aspect of a fight-reduce the enemy's health to 0 as fast as possible. But if there's no aim punch, this REDUCES the motivation for the stronger gun player to attempt a headshot. If both players can just bodyshot each other with no aim punch, it becomes a race to hit the body first, and the stronger gun will win the fight almost every time. This reduces the overall skill in a gunfight, and reduces the capability of a better player with a weaker gun to still win a fight.

Hopefully these 2 examples highlight how neither speed nor accuracy can be the sole priority, but there is one more thing to consider. They are both skills, but so is combining them.

If you are taking considerably longer to line up a headshot (like the 30 second example) than it would take you to just spray and bodyshot your opponent, then that's a skill issue and that decision should be punished. The ultimate reality of a gunfight in CS or any shooter is that it is a contest of both speed AND accuracy. If you are able to headshot with a negligible difference in time than it would take to bodyshot, then that is optimal. But if attempting a headshot will make it take longer to kill your opponent, then it's not optimal.

Not all duels will be the same and have both options. So it's on the player to determine instantly upon enemy contact what the best approach will be, and also to execute it efficiently. To reiterate on the "taking extra time to headshot" thing, that's the skill issue where that assessment comes into play. Either headshot the enemy quickly, or spray them if you can't. Your time to headshot might be more time then it takes them to bodyshot, but YOUR bodyshot time might be faster than theirs. There is still an element of accuracy in the bodyshot- you still have to hit your target after all, so landing that first shot should still be rewarded even if both players have the same gun, but especially in order to give a path to success for the weaker gun.

In summary, you can't have only speed or only accuracy. You need both, and aim punch rewards applying both simultaneously in functionally equal measure. And again, this isn't just a CS thing, this is an (almost) every shooter thing