I think I know how to implement black king bar in a way that offers solid counterplay
You make it so that passively the item will make your champion immune to crowd control if and only if there are at least 2 enemy champions within a short 175 range-- which is only 25 more range than most champion's melee auto attack. The counterplay against that item is to simply move apart from one another.
The discrepency in range and melee auto attack range is to ensure that there can be tense moments where a pair of enemy champions are moving in the same direction away from the light fighter but not apart from one another, and they are barely out of the auto attack range. It would be mere moments before the melee carry catches up or they out run him.
It would offer light fighers a way to corral enemy movement towards one particular location, which gives those champions a way to contribute aside from doing huge amounts of damage. That means that they don't necessiarly have to do gargantuan cheesy damage in order to offer a solid contribution to the team, so they aren't as volatile in a team fight where they are more sensitive to positioning than any other class.
All I am saying is this: If melee carries are going to be the most sensitive to positioning, then they should be rewarded for it moreso than other classes. Currently that isn't the case because the "pieces" on the enemy team can move very quickly and reactively to deny you the proper position you worked hard to acquire.
Riot wants their game to be more reactive than premeditated, but the speed with a team can respond to a new threat is so high it pushes out melee carries. I don't suggest making everyone slower, I just suggest either making melee carries quicker (yasuo) or just making them not so sensitive to the sort of "fast first response" tactics that teams use, which is usually targeted CC or nigh unavoidable CC.
Making an item that grants flat immunity to CC for any duration is out of the question, but attaching it to conditions that the enemy team can control and most importantly, must telegraph, is just what light fighters need to be successful in a team fight.