My house rules don’t mention attacks of opportunity and they don’t limit firing into melee, nor does your movement end if you come too close to somebody armed with a melee weapon. Halberds and Helmets does have a simple protecting allies rule:
Protection: When you are attacked, nearby friends can protect you by placing themselves in the line of attack. The attacker will roll to hit your friend instead of you. You can place yourself in the line of at most one extra attack per round.
This means that most combat ends up having two sides and each side having two rows: a front row, and a back row. Those in front have better armor and melee weapons and they’ll deal more damage because of their strength bonus. Those in the back have no armor and ranged weapons or are casting spells. To protect party members in the back row, you’ll need as many people in the front row as the other side: their front row fighters will all be trying to attack a party member in your back row, and for every one of their attacks, one of your front row fighters will say: “I’m going to take the blow!” If you have a reserve in the back row—well armed or with a lot of hit points—then these can also jump in to protect the weakest party members.
Polearms are easy: you can attack from the back row. If you use a polearm in the front row, that doesn’t mean that you can reach the other side’s back row, though!
Ranged weapons are tricky. For a while, I used to say you could only use ranged weapons when nobody was in melee. You basically had to win initiative in the first round and shoot before the others could close the gap. If you’re lucky, you got to shoot twice if you both surprised your opponents and got initiative. Then I said you could shoot into melee but there’s a chance of hitting your own people, based on the ratio of combatants. This resulted in no change since nobody was ever willing to risk their own. Finally I have begun to say that it didn’t matter. Just fire away and I’ll assume decent positioning and all that. Can you shoot into the back row? Yes you can. Can you shoot through your own front row? Yes you can. It’s like stabbing through your own front row with a polearm. 🙂
How do other games do it, though? This is what Ryuutama says:
Enemy Back Area: A character must be equipped with a bow or use long ranged magic in order to attack a Monster in the Enemy Back Area.
Front Area: In the Front Area, enemies and allies alike join in close combat. Using spears, blades and axes, you can attack monsters in the Front Area. Spells or effects that target an area will affect both enemies and allies in this area. Characters in the Front Area can be attacked by ranged or magic attacks from a Back area.
Back Areas (Enemy/Ally): The Back Areas are separated from the Front Area, safe from close combat. If the Front Area is totally clear of enemies, all combatants in the Enemy Back Area will automatically be moved into the Front Area. Likewise, if no allies remain in the Front Area, all allies in the Ally Back Area are moved into the Front Area.
Take a look at the Battlefield Sheet in order to visualize the setup. The net result is that where as you’re “safe from close combat” in the back area, ranged attacks can target people anywhere. And that’s how my D&D works, too: ranged combat can hit anybody on the battlefield.
Ryuutama’s protection rule is very different, however:
Defend: A character may choose to focus completely on defense. Until the character’s next turn, whenever they take damage, the damage they receive is reduced by one. In addition, this character may decide to become the target of any attack aimed at an ally in the same area. If they decide to do so, the attack automatically hits.
The benefit seems to be that you can become the target of more than one attack. But they all hit. In D&D, they would all do full damage. In Ryuutama, armor acts as damage reduction, so perhaps that’s not so bad, after all.
Now watching: Ryuutama: Character Creation (14½ min)