A quick homebrew about firing into close combats.

Current Rules for firing into close combats are: You may not fire into CC if one of your models is in close combat. If firing into another close combat where none of your models are involved, randomize the hit among the models in the close combat.

Proposal:

Nominate a close combat to fire into. If the close combat involves one of your models, the firing model must make a Leadership Check to fire into the ensuing fight.

Nominate an enemy warband in the close combat to fire into. Roll to-hit, with a -1 BS penalty.

Should the shot hit, roll a D6, taking any modifiers below into account.

+1 The target warband has at least one Large model in the close combat.
+1 The target warband outnumbers its enemies in the close combat.
-1 The target warband is outnumbered in the close combat.
-1 The target warband is fighting at least one Large Model in the close combat.

On a 4+, the attacker may select one model in the close combat from the enemy warband to take the hit.  Otherwise, the defending player may select any model in the close combat to take the hit.

Skaven get the special rule Life is Cheap: Heroes do not count Henchmen as friendly models for whether or not they have to take a Leadership check to fire into Close Combat.

Optional Shooting Skill: Trigger Discipline: A model with Trigger Discipline ignores the -1 BS penalty to fire into Close Combats, and may reroll the d6 to see whether the attacker or defender allocates the hit.

The implications of these rules would be admittedly interesting, simply because of the risk/reward of being able to knock-down/stun models already engaged in combats.

This is a delicate area to tread around. While it would make sense to be able to shoot into any close combat you want, being safe from enemy shooting while in combat is a big part of the balance between fighting and shooting warbands. Being able to pick your final target after the hit roll would also be a big No from me, since that will enable the sniping of important models. Randomization would be better if you're going with this house rule.

It's a "partial" randomization of a sort. The idea being that in theory, if one of your henchmen is up against 3 zombies or so, odds are a bit higher you will hit a zombie instead of your own guy. Inversely, if your Troll is trying to chase down a Halfling scout, you don't want your Goblins to fire into the fray!

It loses a lot of the randomization when you get to pick exactly which model is hit after you've rolled to determine which side is being hit. Your proposed Trigger Discipline skill makes it much worse still, making it a pretty good bet that you will be hitting the enemy side and you then get to choose your victim. I just know my vampire would be focused down way too hard with this, and I wouldn't like playing against it.

Is there anything against using straight randomization for this instead? As in, assign a dice score for each combatant and on that roll they're the one being hit. Large targets could take up two separate scores to make them more likely to be hit.

I'm still not friends with the idea of being shot at while in combat, but if it were implemented I think there should be some additional potential consequences for the shooting warband. I imagine that accidentally taking your own buddy out of action would be quite demoralizing. It should be more of a desperate last attempt at salvaging a situation, since I don't think strong shooting warbands need more help.

I have some slight personal bias against "randomly determine the model in the unit that takes the hit" effects, mostly due to edge cases from 40k ("randomly determine the model hit in a unit of 29 orcs" or something similarly weird).

That said and done, I like your idea for straight randomization better. Rather than making trigger discipline a reroll to see who allocates the hit, make it a straight reroll to which model gets randomly hit.

Considering this is meant to be intentionally risky and chaotic, I'm all for making it a desperate attempt to salvage a situation.

I agree it would make a big impact in the balance between shooty and close combat oriented bands.

In chaos on the streets supplement there are some "rul" about shootimg to melee:

Shooting into close combat:
Unlike in the regular Mordheim rules, it is possible to shoot into close combat in multiplayer games, just as long as the shooters belong to a different warband than the models involved in the Close Combat.Shooters must still fire at the closest enemy model as normal(unless they are in an elevated position, as per the normal rules). However, if the shooter hits a model involved in a close combat, the shot may well hit one of his opponents and not the model itself. Randomize any missile hits between the target and any models in close combat with him.

It is also suggest randomizing.