Short answer: This is an okay solution.
Longer answer:
This is a pretty good solution, but you have issues like some armies not having any real countercharge units (tau), and you'd have to decide whether or not to let models with Fly fall back before the shooting phase per the current rules (and if not, how much of a points cost reduction is that worth?)
My preferred solution is to say that enemy units that began the turn within 1" of one of your own units cannot be shot at by units that are more than X" away . And then have x = 9 or 12 or something. The idea being that gunlines end up having to reduce their offense and move towards your units in order to shoot at units that were fallen back from. Alternatively, gunlines can counter this by clumping up, but that makes them even more susceptible to having multiple units tied up at once.
I think most of us explored this subject pretty thoroughly here if you're interested:
https://www.dakkadakka.com/dakkaforum/posts/list/788521.page