I was checking on something else and happened to verify that they already do exactly this on Live. In Stone Hive, they have a bunch of NPCs wielding weapon models that are not in their loot table and they do show the correct message types when attacking like "slashes", "crushes", etc.
I think the best way to do it might be to use the attack types we already have defined and create 2 new fields in the npc_types table like "prim_atk_type" and "sec_atk_type".
Also, to do what ChaosSlayer is wanting, we could just have an extra field that overrides any other attack message type if it is set. A text field like "atk_type_msg" that you just put the attack type message such as "tailwhips" or "bites" or "scratches" or you get the picture
