Horsies Shall Be Splintered!

OK, maybe "splintered" is the wrong word, here. But when Delta's Hotspot had a post on cavalry in D&D, it occurred to me that you could follow more or less the same rule as for Trollsmyth's "Shields shall be splintered": a player can say that damage from a successful hit against their mounted character hits the mount instead. They have to invoke this rule before damage is rolled, and the rule doesn't apply to aimed attacks, just general melee.

I haven't looked at mounted combat rules in detail yet, but I have a few other ideas:

• One benefit of mounted combat is that the rider's attack is distinct from the mount's movement; in other words, the rider can attack anywhere during the move, usually expressed as taking half move, attacking, then moving again. This isn't explicitly stated in the LBBs, but it's implied in the entry for Elves; the point about elven "split move and fire" is that elves are so good with archery that they can fire while moving on foot as if they were mounted archers. Instead of specifying half-moves, I think I'll just go with a rule that mounted figures (and elven archers) can fire at any point during movement, with missiles fired before traveling a distance more than half the movement rate striking before general melee.
• A mounted charge is treated as mounted missile fire (split move and fire) unless the rider or mount is struck or unhorsed; in other words, the mounted attacker can moved beyond the point of attack up to the full movement rate.
• During a charge, longer weapons strike before shorter weapons, the inverse of melee attacks. Also, treat the mount and rider as a single attacker: add the hit dice of the mount to the attacker's hit dice to determine chances to hit.
• While mounted, a rider can opt to attack with their horse instead of their weapon. The main benefit of this is that a medium or heavy horse combined with a rider is treated as an ogre for damage purposes (1d6+2 instead of the usual flat 1d6.)
• Footmen with shorter weapons attack mounted opponents at a disadvantage (-1 to attack) because of height.
  
• If the rider dismounts in combat, most horses will only defend themselves when attacked and need to roll for morale. Warhorses can attack random foot soldiers, although normal hireling morale and command control rules still apply. A rider cannot designate another person as his sergeant for purposes of commanding his horse for a distance; the horse responds to simple commands/gestures from its master only.

I'd handle a lot of other things in mounted combat, like overrunning footsoldiers or trying to unhorse an opponent, as if they were combat tricks, with Change Situation or Avoid Accident rolls; the damage roll becomes a d6 roll to see if the footsoldier is knocked down or the rider pulled from the mount.