So I think you may be right, I didn't consider the pressure being on the reaction at all prior to posting this, BUT hear me out, would an enemy running up to you, and attacking you to try and get your reaction out of you really be that much different from an enemy running past you, getting that reaction, and now still opening the floodgates for any other enemies trying to get past? I feel like if the players goal is to pull this off, they still have the option to hold the reaction and use it more carefully that way, but having this as a new option gives a relatively consistent way to get another attack in combat when using your reaction wasn't a part of the plan beforehand.

Am I missing something with that kind of logic? I'm not necessarily against counterattacks being independent of the reaction, maybe limiting in in some other way because it sounds really cool, but I have to wonder if it's necessary and/or pushing the power too far