It's not cheese, when the bad guy is standing near a safety hazard it's the logical thing to use that to defeat them, at least that's how it works on tabletop. Pushing villains into a pit/volcano/off a cliff is a staple of stories.
I just hate restricting options when they're already incredibly restricted because it's of a video game format.
But it is indeed a VideoGame with Fixed Values, Mechanics, Tweaked Randomizers and it affects Balance. This is not Table Top where you can make stuff up as you go like throwing a Banana and rolling for that Lvl 99 Evil ArchMage to slip all the way to his Death.
But a Hard Dialogue Check that ends up with the NPC's Instant Demise? I guess that could be affordable. Should give you your whole "This is Sparta" Special Cutscene and the like. But the whole Shoving Mechanic Concept is already broken as it is just like Frog Backstabbing was. I mean, it's not like they are taking away Exploding Barrels and Throwable Spam?