They should just put them under small guns and big guns, which would make more sense. Then they could just make it harder to get those stats.
Doing this would eliminate a Skill and create more weapons for the above two Skills. It wouldn't be smart. What would they replace Energy Weapons with?
IMO
Small Guns --- A weapons that requires one hand or is within a certain length limit. It may also class a weapon that can only shot 1 round per second (in FO3) E.G. It would be unwise to class a Revolver as a Big Gun, while it would be just as stupid to class a Minigun as a Small Gun.
Big Guns --- A weapon that needs to be mounted onto something, or needs bracing before being used. Obvious examples are the Minigun and RPG. More examples are the Stationary Guns from WW2 and the .50 Cal on some jeeps.
Energy Weapons --- A weapon that fires an Energy "Slug". These weapons do not use conventional ammo and some may use unstable Energy Sources (A good example is from UFO-Enemy Unknown. What is Compound-115 made of? And why is it stable enough to be used in a Weapon?). Good examples of Energy Weapons are Pulse Weapons, Laser Weapons, Plasma Weapons etc.