It’s pretty clear how melee weapons work in an advancing formation down a typical “three may walk abreast” dungeon corridor: a group of three swordsmen/spearmen with shields out front, a second line of three pikemen behind them, and then some casters in the third row. And if someone out front wants to swing a big sword around, then the front line is only two wide.
Where do thrown and missile weapons fit here, or tossed splash weapons like flaming oil and holy water? Can they fire from the second row? The third row? Are they in a row of three, or two, or does it depend on the weapon type?
What about a fourth row? Is there any point at which even spellcasters are so far back they can’t make visual contact to pick targets?
In my own games, I typically allow thrown and missile fire from any/all ranks up until targets become engaged. ACKS is already relatively punitive about firing into melee, compared to most other fantasy games. .
If you wanted to be more realistic about it, you’d have to take into account ceiling height, arc of fire, and line of sight. Bows could fire from virtually any rear rank if there was sufficient clearance overhead. Crossbows could fire regardless of ceiling height but would need relatively clear lanes of fire.
The funny thing about restricting missile fire into melee is that it affects monsters in almost all situations except for narrow corridor fights. In a narrow corridor it’s hard to get into contact, due to the chokepoint. So there are third-row combatants on both sides who will be volleying arrows and chucking axes at one another right over the top of the melee, in a way that wouldn’t happen if the battle were in a more open room where everyone was engaged.
This isn’t necessary bad from the standpoint of game flow (pretty boring if the back-row guys just have to stand around and watch, after all), but it feels odd from a simulationist standpoint.
But I agree that trying to fix that would send you down a deep rabbit hole.
From a simulationist standpoint, it seems reasonable that you would be willing to use dangerous, unpredictable weapons like flaming oil in scenarios where the lines of battle are clearly drawn. I’m pretty confident in my ability to throw something 15 feet over my friends into a big pile of enemies; I’d be less confident about my ability to hit the right guy in a tavern brawl.