Buff SMGs that the first 7 bullets fired are near accurate (say 70%, but it may vary), but after that, have them be CFX50 hipfire inaccurate such that continuous spray at anything but close range is a liability. To regain the original accuracy, release mouse1 for ,lets say, 0.7 seconds (this will also vary between SMGs).
This might make SMGs overtake the sniper in CQB, but the snipers will now have an edge over the SMGs in long ranges, as it should be. If the sniper can still get the SMG player in CQB, it will be a difference in skill.
technically that is similar to the new call of duty recoil mechanic lol
it applies to all guns tho