I’ll keep it simple
What messes up a Snipers shots? Aimpunch, who does it currently affect the most? Everyone BUT the Sniper
How do you fix it? Remove the aimpunch that affects your crosshair movement, but keep the visual shake. So when you are hipfiring, you can still tell when you are being hit. However when aiming, you have the actual aimpunch, which will affect your crosshair’s movement.
To compensate for this, increase recoil on guns, and have ADS reduce or minimize recoil and spread in exchange for loss of movement and aimpunch affecting your aim.