The problem with just buffing the stats of the MS without changing the effect is that the effect is almost completely useless. It's not even that much of a pushback and if you buff the effect you still end up with a questionably useful one. On the other hand the kinetic effect makes it hard to put this on hostile fighters.
On difficulties below insane the player is going to be much harder to kill meaning a gun config focusing on pure damage won't work as well thanks to the huge survivability buffs the player has and the firerate penalties for the AI. So just knocking them around with kinetic weapons or wasting their time with EMPs can be pretty effective and somewhat frustrating.
Against things that are actually hostile why would you want to push them away outside your tempest range when you can just take the Prom S and kill them?
So if you only buff the stats you end up with a decent DPS gun with a reasonable energy cost. So you take it over the Subach just for the stats and then later switch to prom S, again, just for the stats. The core question for FS2 and BP-era weapons will always be "Why would I want this over the Prom S or Balor?" And if you make something better than those guns on raw stats then it'll just become the new measuring stick. That's why most weapons were given some unique selling point that might make you want to actually use them over the balanced stat kings of the PromS and Balor.
Sure, you could add a non-zero blast force to the shockwave or a kinetic effect on direct hits just to stay somewhat consistent with that one Cbrief but you go back to the problem of it being far more powerful against the player than when being used by the player. I mean, most players probably wouldn't even notice if it did have a small kinetic effect in the shockwave since it deals actual damage now. For ships to really veer off course you need a lot of consecutive hits. You hit something a lot with this Morningstar and it will probably just die. And then you could table a new Morning Star#hostile that has no kinetic effect and is fine to put on hostile ships. But that's a lot of added complexity to stay consistent with one Cbrief.