Though not exactly necessary, I feel that headshots would bring a little more to the mod. There are probably a few ways to implement this feature.

1. Two separate damage variables.
   Damage 15
   HeadshotDamage 10000
   This would mean that content pack makers (such as me) would have to go through all of his/her weapons and add the HeadshotDamage variable into the files.
2. A fixed multiplier hardcoded into the mod. This would mean that there would be less freedom in content packs, but existing content pack makers wouldn't have to go through all of their guns and add the HeadshotDamage variable.
3. Both. If a content pack maker wants to have a base damage of 0 and a headshot damage of 9001, then (s)he can do that. But if (s)he already has the base damage at 9 and (s)he wants to use the multiplier (or (s)he is just too lazy to add in the HeadshotDamage variable), then the headshot damage will be set to damage*1.5 (or something else) by default.

Headshots are implemented and currently do double the damage however there are not plans to make the mulitplier configurable for the time being.