In fact I do not have enemies carry weapons. I actually don't use the weapon system and ended up just using the "no_weapon" weapon for the player :p
BUT it was coded with enemies having weapons in mind. So in the body family I have a variable caled "body_team".
So I have enemies and heroes being on diferent teams so each one can only aply damage to the oposite team. Is that what you're looking for?
-- edit
jwilkins
I guess I miss read what you said. You want enemies with no weapons to have diferent atack animations when having no weapon?
In that case the anemies with no weapons would just have diferent animations but would use the same weapon overlay for the no_weapon kind of weapon.
If you want diferent enemies to have diferent atack types and colisions I would just equip the enemy with a "diferent kind of no weapon". You could add weapons like: no_weapon_punch, no_weapon_punch2, no_weapon_kick, etc...
With every "no_weapon" kinda of weapon with diferent colisions and animations... Yeah, I guess that's pretty much it, thats how I would do things. Have you ever player little figther? They have a system that is pretty similar to the one we're talking about. I recommend you to check it out, it's a pretty cool game/system.