Just do it like in Solasta... you can either shove prone or shove 5 feet away, as an action, or part of attacks. Like in PHB. Done.
"Just do like in Solasta" solves pretty much every problem with BG3's combat.
BG3 EA combat is way more varied and interesting than Solasta’s IMO. I understand some complaints about 5e implementation, but Solasta’s enemy behavior is incredibly dull. Being sometimes frustrated by a shove KO is still better than having enemies that just attack the closest for 90% of the time.
+1
Solasta has such horrible encounter design too, the very first battle in the DLC starts with a bear just appearing out of nowhere right next to your party. And it has a decent chance of just instantly killing a character.
BG3 combat is more fun than Solasta in pretty much every way that matters.