Comment 2 for bug 895270

I think this would make more sense if it were controlled globally rather than per-weapon, like this:
[General]
FallDamage=20 ;base damage applied to a dropped unit
FallDamagePerCell=20 ;additional damage applied per cell height dropped
FallDamageWarhead=FallDamageWH ;the warhead used to apply the damage to the dropped unit. This can include a sound/impact anim/etc (although impact anim should only be shown if landing on empty ground)
...with the values defaulting to zero of course