It's an easy fix.
Give the option of the firefight (and have it be almost impossibly difficult), then have the opposing forces execute the civilians if you choose that option. It establishes narrative chops of the futility of trying to save *everyone* in a war, still gives indirect blame, and adds more gravity on another playthrough if you *do* use the white phosphorus. The choice being between the difficulty of inevitability (and the consequences of being stubborn in a war scenario) and the ease of monstrosity (which thematically is what the use of drones represent in a position of power). Does a better job of putting you in that Kurtz-like position that they sit you in at the end of the game.
Still loved the game, though.
Give the option of the firefight (and have it be almost impossibly difficult), then have the opposing forces execute the civilians if you choose that option. It establishes narrative chops of the futility of trying to save *everyone* in a war, still gives indirect blame, and adds more gravity on another playthrough if you *do* use the white phosphorus. The choice being between the difficulty of inevitability (and the consequences of being stubborn in a war scenario) and the ease of monstrosity (which thematically is what the use of drones represent in a position of power). Does a better job of putting you in that Kurtz-like position that they sit you in at the end of the game.
Still loved the game, though.